Genome size variation in the Poaceae supertribe Poodae, the major grass lineage of temperate climates (tribes Aveneae, Festuceae and Poeae)

doi:10.21203/rs.3.rs-5003188/v1

Download PDF

Research Article

Genome size variation in the Poaceae supertribe Poodae, the major grass lineage of temperate climates (tribes Aveneae, Festuceae and Poeae)

https://doi.org/10.21203/rs.3.rs-5003188/v1

This work is licensed under a CC BY 4.0 License

You are reading this latest preprint version

Nuclear DNA amounts were examined by flow cytometry for 70 genera and 214 species and subspecies taxonomically belonging to the supertribe Poodae of the grass subfamily Pooideae. This supertribe contains most of the grasses distributed in the temperate extratropical regions of the world and is important because of its many cultivated species (e.g., grains) and its prominence as a major component of grasslands. The majority of holoploid genome sizes (2C values) ranged from 5 to 10 pg, with the full range of values representing a 30-fold variation. Most monoploid genome sizes (1Cx values) were between 2 and 3 pg, with a total of 12.3-fold variation. The minimum values in Poodae are only about twice those of Brachypodium stacei, which has the smallest genome known for the subfamily Pooideae, and those of rice and some other species of the rice subfamily (Oryzoideae) and a few species of the subfamily Panicoideae with miniature genomes. The maximum values of our study group are among the largest found within the whole family Poaceae, only slightly surpassed by a some in the tribe Triticeae (wheat and related species). The effects of polyploidy and dysploidy, their association with genome “downsizing” as well as with cases of size increase, were analyzed in both autopolyploids and allopolyploids. The origin of the low chromosome number of only x= 2 in some Poodae species and the transition from perennial to annual life form were addressed in the light of genome sizes, which were also discussed in a phylogenetic framework.

Dysploidy

C-value

Chromosome base number

Life form

Polyploidy

Pooideae

Eukaryotes have highly variable genome sizes, which can be measured as the length of the genome expressed in base pairs or as physical mass in grams. The genome sizes of grasses, one of the larger angiosperm families, range from 0.42 pg in the diploid Panicum gilvum to 45.26 pg in the decaploid Thinopyrum ponticum (Vogel et al. 1999; Chen et al. 2021), where these values (2C values) represent the DNA amount of DNA from non-replicated sporophytic cell nuclei with the chromosome number 2n. The chromosome number of P. gilvum is probably 2n = 2x = 18 with 9 chromosomes in a single monoploid chromosome set with the chromosome base number x, that of T. ponticum is 2n = 10x = 70 with x = 7 (Vogel et al. 1999). The approximately 108-fold difference in genome size in grasses is therefore obviously not only due to the number of chromosome sets present in the nuclei (ploidy), which is only 5-fold different in the two example species (diploid vs. decaploid). The main source of variation is the different amount of DNA in each chromosome, with repetitive DNA being a highly variable component, while the actual coding DNA (genes) does not show such dramatic variation between species (Ibarra-Laclette et al. 2013; Orozco-Arias et al. 2019; Ramakrishnan et al. 2012; Mhiri et al. 2022; Moreno-Aguilar et al. 2022; Kong et al. 2023). For example, the sequenced genomes of Brachypodium, Panicum, and Setaria species show an overall similar proportion of coding sequences between 31 and 42 Mbp, while the total amount of repetitive DNA varies between 41 and 463 Mbp. The largest contributor to the observed variation in repetitive DNA was LTR retrotransposons, followed by TEs (Lei et al. 2024). As genomic units that can move around the genome, transposable elements were initially considered “junk DNA”, but they have since been shown to play key roles in chromosome structure, gene expression and regulation, to be associated with genome rearrangements and specific chromosome features, to act as insertional mutagens, and to play essential roles in transcriptional regulation and networks, for example, in the course of biased genome fractionation following whole-genome duplications (Ågren and Wright 2011; Bourque et al. 2018; Serrato-Capuchina and Matute 2018; Anderson et al. 2019; Orozco-Arias et al. 2019; Baduel et al. 2021; Pellicer et al. 2021; Catlin & Josephs 2022; Colonna Romano and Fanti 2022; Pulido and Casacuberta 2023; Beringer et al. 2024). The role of TEs as endogenous drivers of gene expression makes them an significant factor in adaptation to environmental conditions such as heat, cold, drought and herbivory. This makes genome size an important trait that affects many characteristics of organisms, independent of the genetic information encoded, such as cytological (DNA replication, cell size), functional, phenotypic, and organ size-related traits that influence metabolic and physiological performance as well as macroevolutionary patterns (Bennett 1972; Greilhuber 1995; Leitch and Bennett 2007; Greilhuber and Leitch 2013; Kang et al. 2015; Meudt et al. 2015; Carta and Peruzzi 2016; Souza et al. 2019; Trávníček et al. 2019; Meyerson et al. 2020, 2024; Novák et al. 2020; Cacho et al. 2021; Han et al. 2020; Plačková et al. 2021; Van de Peer et al. 2021; Carta et al. 2022; Théroux-Rancourt et al. 2021; Schley et al. 2022; Bhadra et al. 2023; Yang et al. 2023; Bureš et al. 2024; Hlavatá et al. 2024; Pinto et al. 2024; Valdés-Florido et al. 2024; Záveská et al. 2024). It has been shown in a wide range of plant families that changes in genome size have substantial consequences at the cellular, tissue, and organismal levels, influencing phenological and ecological behavior and thus providing useful information for the understanding plant evolution and diversification (Bennett 1972; Caetano-Anollés 2005; Greilhuber and Leitch 2013; Pellicer et al. 2018; Doyle and Coate 2019; Qiu et al. 2019; Cacho et al. 2021; Faizullah et al. 2021; Pfanzelt et al. 2021; D. Wang et al. 2021; Zhang et al. 2023).

Evolutionary history. The family of grasses, apart from a few ‘early-diverging’ lineages, comprises two major phylogenetic groups, one of which, is the so-called BOP clade, which consistently has the C₃ pathway of photosynthetic carbon dioxide fixation. The BOP clade includes the subfamilies Bambusoideae (bamboo grasses), Oryzoideae (rice subfamily) and Pooideae, which is the largest subfamily of grasses with 219 genera and 4126 species (Soreng et al. 2022a) and is typical of temperate to cool climates, thus dominating the northern hemisphere. The BOP clade originated in the Late Cretaceous about 80–90 Ma ago (Schubert et al. 2019; Gallaher et al. 2019, 2022; Orton et al. 2021; Huang et al. 2022, Zhang et al. 2022) under a warm global climate with little difference between high and low latitudes, no frost, and little or no climate seasonality. The Late Eocene brought a gradual cooling of the climate, leading to the expansion of temperate climates and finally, at the Eocene-Oligocene transition 34 Ma ago, to global cooling with increased climate seasonality. The increasing diversification of the subfamily Pooideae, showing clear adaptations to temperate climate, was associated with the Cenozoic temperature drop and expansion of temperate biomes (Schubert et al. 2019). Diversification continued in the Miocene and Pliocene, producing primary grasslands in both hemispheres (Edwards et al. 2010; Pimentel et al. 2017).

The largest group of Pooideae is characterized by a chromosome base number of x = 7 (‘core Pooideae’), a lineage that is widespread from the Mediterranean to the Arctic, represented on mountains of the tropics and regions of the southern hemisphere with temperate climate (southern Africa, South America, the cooler regions of Australia, New Zealand, and the subantarctic islands to Antarctica).

The ‘core Pooideae’ is divided into two phylogenetic lineages, one of which, taxonomically treated as the supertribe Triticodae, includes wheat (Triticum) and its relatives such as brome grass (Bromus), the other as the supertribe Poodae, which comprises many species-rich and presumably actively evolving genera typical of Holarctic and boreal vegetation, such as Agrostis, Calamagrostis, Festuca, Koeleria, Poa and Puccinellia, together containing more than 1,700 species. The group originated in the Middle Eocene about 41 Ma (stem age) ago, had its early diversification at about 36 Ma and continued to diversify into numerous lineages from about 29 Ma onward (Gallaher et al. 2022). Most of these are Miocene, some are less than 10 Ma old, and of Late Miocene to Pliocene age, including the large and widespread genus Poa and related genera important for Holarctic flora such as Alopecurus, Phleum, Puccinellia, etc. (Hoffmann et al. 2013; Soreng et al. 2022b). Much of their intense speciation, often involving polyploid speciation and apomixis, is therefore contemporaneous and likely due to the Late Pliocene and especially Pleistocene climate fluctuations and corresponding shifts of climate and vegetation zones, especially in the Northern Hemisphere (glacial-interglacial cycles), which also promoted the expansion of cold-adapted species in many other angiosperm families (Tkach et al. 2008, 2014, 2019; Hoffmann and Röser 2009; Hoffmann et al. 2010; Ebersbach et al. 2017; Kadereit and Abbott 2022).

Biosystematic background. The supertribe Poodae, with about 142 genera and 2562 species worldwide, is taxonomically considered to comprise the single tribe Poeae (GPWG 2001; GPWG II 2012; Kellogg 2015; Saarela et al. 2015; Soreng et al. 2017, 2022a). Based on sequence analyses of plastid DNA, the Poeae genera were grouped into two distinct lineages, which were concordantly found by Sanger and whole-genome sequencing analyses (Davis and Soreng 2007; Quintanar et al. 2007; Schneider et al. 2009, 2012; Saarela et al. 2015, 2017, 2018; Orton et al. 2019, 2021; Tkach et al. 2020) and did not agree with the segregation of the traditional tribes Poeae and Aveneae. However, nuclear DNA sequence studies based on Sanger markers, single copy gene and transcriptome analyses resolved lineages that were partly different from the plastid DNA groupings (Table 1) (Tkach et al. 2020; Huang et al. 2022; Zhang et al. 2022). Using as complete a set of associated genera as possible and a taxonomically overlapping set of plastid and nuclear DNA data, an alternative taxonomic treatment of the supertribe Poodae was proposed by recognizing three subtribes with partially revised circumscriptions, namely Aveneae, Festuceae, and Poeae (Tkach et al. 2020: p. 255). This clade structure was also reflected in nuclear transcriptome analyses, in which Aveneae and Poeae appeared as the two major lineages of ‘Poeae nuclear group I’ (PNG I) and Festuceae as ‘Poeae nuclear group II’ (PNG II), named by Zhang et al. (2022).

Each of the tribes Aveneae, Festuceae and Poeae contains several subtribes, which are color-coded in Table 1. However, seven subtribes of the Poodae (Airinae, Antinoriinae, Aristaveninae, Helictochloinae, Holcinae, Scolochloinae, Sesleriinae), cannot be unambiguously assigned to one of the three tribes because of conflicting phylogenetic signals between the plastid and the nuclear DNA-based molecular phylogenies (cytonuclear discordance), indicating a possible hybrid origin in evolutionary terms (Tkach et al. 2020: Fig. 7). These conflicting phylogenetic signals also emerge from phylogenomic plastid and nuclear low-copy gene and transcriptome data (Saarela et al. 2015, 2018; Orton et al. 2019; 2021; Huang et al. 2022; Zhang et al. 2022). In some cases, no clear phylogenetic position could be determined due to insufficient resolution of the plastid and nuclear DNA trees.

To the best of our current knowledge, the phylogenetic ‘roots’ of the subtribes Airinae, Antinoriinae (Antinoria only), Holcinae (Holcus, Vahlodea), Scolochloinae (Dryopoa, Scolochloa) and Sesleriinae (six genera) suggest an ancient hybrid origin between ancestors of the tribes Aveneae and Festuceae, listed as “Incertae sedis” subtribes in Table 1. Those of the subtribes Aristaveninae (Deschampsia only) and Helictochloinae (Helictochloa, Molineriella), however, are more indicative of hybridization between the tribes Festuceae and Poeae, as revised from our previous conclusion (Tkach et al. 2020: p. 255). Past hybridization between Aveneae and Poeae has not yet been detected, as previously noted (Tkach et al. 2020). The above seven subtribes have been treated as taxonomically unplaced taxa and named ‘intertribe hybrids’ to denote their reticulate evolutionary origin.

Cases of deep hybridization also occur in several other taxonomic groups within the supertribe Poodae (Tkach et al. 2020). The subtribe Avenulinae has a hybrid origin between ancestors both belonging to the tribe Poeae, while the subtribes Anthoxanthinae, Phalaridinae and Torreyochloinae as well as Macrobriza maxima (syn. Briza maxima) have a hybrid origin between ancestors both belonging to the tribe Aveneae, and Arctopoa has a hybrid origin between different lineages of the tribe Poeae (see above).

To resolve the remaining phylogenetic uncertainties, more comprehensive nuclear DNA data and a more complete taxon sampling would be very useful for a reliable, molecular phylogenetically validated taxonomic classification of the Poodae and the subtribes mentioned. This is because the nuclear genome contains the vast majority of genes and is largely responsible for the morphological, physiological and developmental characteristics of organisms compared to plastid DNA. This means that the nuclear genome is ultimately the cause of the existing morphological diversity and complexity of species, which has always been the basis for systematics and classification of taxa.

Chromosomal and genomic research in the ‘core Pooideae’ focuses on Triticodae due to their enormous significance in crop plant research (e.g., Miedaner and Korzun 2018; Pont et al. 2019; Tadesse et al. 2019; Bernhardt et al. 2020; Walkowiak et al. 2020; Feldman and Levy 2023b). Cytogenetic and genomic research has focused on the genus Avena (oat) and a comparatively small number of other exemplary genera such as Aira, Anthoxanthum, Deschampsia, Festuca, Helictochloa, Helictotrichon, Phalaris, Sesleria, etc., which have been studied mainly with respect to chromosome structure and polyploid evolution and Colpodium (including Zingeria), which has species with particularly low chromosome numbers ranging from 2n = 4 to 2n = 12 (Kotseruba et al. 2005, 2010; Kim et al. 2009; Winterfeld and Röser 2007a, b; Winterfeld et al. 2009a, b, 2012, 2018; Chumová et al. 2015, 2021; Lazarević et al. 2015; Wölk et al. 2015; Mereďa et al. 2019; Hodálova et al. 2020; González et al. 2021). Quantitative analyses of genome sizes have revealed examples of intraspecific and interspecific differences in various genera of Poodae such as Anthoxanthum, Avena, Festuca and Lolium (Murray et al. 2005; Kopecký et al. 2010; Yan et al. 2016; Chumová et al. 2015, 2021; Rios et al. 2015; Garnatje et al. 2023). This variation has often been correlated with adaptation to different environmental, especially climatic conditions, for example in species of Dactylis, Festuca and Koeleria (Reeves et al. 1998; Pečinka et al. 2006; Šmarda and Bureš 2006; Šmarda et al. 2008; Martínez-Sagarra et al. 2021).

Although there are about 760 estimates of DNA C-values in Poodae (Leitch et al. 2019), the full range of variation is still unknown, and the consistent occurrence of large genomes is by no means certain. The present study aims to address the following questions: (1) What are the sizes and variability of nuclear DNA amounts in the supertribe Poodae? (2) Does dense sampling of the larger phylogenetic groups, as well as consideration of smaller units as fully as possible, reveal differences among evolutionary lineages? (3) How do the genome sizes of the Poodae compare with those of the better studied Triticodae, which also have x = 7, and with those of the other tribes of the subfamily Pooideae and the other subfamilies of grasses? Can large genomes be confirmed for the Poodae? (4) How does variation relate to polyploidy and the often observed reduction in genome size in polyploids (‘genome downsizing’), and how does it relate to dysploidy, a stepwise pattern of numerical change in chromosome number occasionally found in the Poodae. (5) Finally, how does genome size relate to changes in life form, especially the transition from perennial to annual life cycles.

Plant material

Our sample studied for genome size included 399 accessions from 214 species and subspecies in 70 genera (Table 2; Online Resource 1). One to 10 accessions were examined per species studied. Data were recorded separately for each accession in Online Resource 1, but were averaged in Table 2 when multiple accessions of a species were sampled, provided they belonged to the same cytotype/ploidal level (mean value, hereafter abbreviated as MV). In terms of taxonomic completeness, the sampling included, representatives of 50% of the genera of the supertribe Poodae, belonging to all three of its tribes accepted here and 27 of the 33 subtribes (Table 1).

Fresh leaves for the genome size measurements were collected in the field, from living potted plants of our greenhouse research grass collection, or from the plant collections of the Botanical Garden of the University of Halle-Wittenberg. Leaf samples were either processed immediately or stored in plastic bags with moist tissue in a refrigerator at 4°C for up to five days until processing. Silica gel-dried leaves, preferably stored at -20°C or -80°C, were also successfully used. Voucher specimens of most accessions have been deposited in the herbarium of the University of Halle-Wittenberg (HAL). Details of the provenances studied and the type of the plant tissue used for the experiments, whether fresh or silica gel-dried, are listed in the Online Resource 1.

Measurement of genome sizes

Genome sizes were estimated by flow cytometry (FCM) following the protocols of Doležel et al. (2007), Sliwinska et al. (2022) and Loureiro et al. (2023) with minor modifications (see Tkach et al. 2024). Briefly, after grinding the plant material of the test plant together with the DNA standard plant, cell nuclei were extracted and stained with propidium iodide (PI) using the CyStain PI OxProtect reagent kit (Sysmex Partec GmbH, Görlitz, Germany) according to the manufacturer’s protocol. A CyFlow Ploidy Analyser (Sysmex Partec) with a 532 nm green laser was used for excitation and signal detection. Measurements were stopped after a minimum of 3,500 nuclei and replicated three times with quality control of histograms and calculation of the test plant genome sizes as previously described (Winterfeld et al. 2023, 2024; Tkach et al. 2024). The following standards, with their 2C values in brackets were used for all individual measurements as indicated in Online Resource 1: Glycine max Merr. ‘Polanka’ (2.50 pg), Pisum sativum L. ‘Ctirad’ (9.09 pg), Raphanus sativus L. ‘Saxa’ (1.11 pg), Secale cereale L. ‘Daňkovské’ (16.19 pg), Solanum lycopersicum L. ‘Stupické polní rané’ (1.96 pg), Vicia faba L. ‘Inovec’ (26.90 pg) and Zea mays L. ‘CE-777’ (5.43 pg).

Previously published DNA C-values were obtained from the ‘Plant DNA C-values Database’ (Leitch et al., 2019; Henniges et al. 2023; https://cvalues.science.kew.org/) and Bureš et al. (2024: Supplementary Dataset S1), with the original publications also consulted in all cases.

Chromosome numbers, monoploid genome and mean chromosome sizes sizes (1Cx values and MCs)

For many accessions used for genome size estimation, chromosomes were also counted in this study or in previous studies by our laboratory, as listed in Online Resource 1. In the other cases, the chromosome numbers were compiled from the ‘Chromosome Counts Database’ (CCDB: see Rice et al. 2015; Rice and Mayrose 2023), the ‘Index to Plant Chromosome Numbers’ (IPCN 1979 onwards) or cited from original publications (see Results and Discussion and References).

Monoploid genome sizes (1Cx values) were calculated for species with known chromosome number or ploidy by dividing the 2C values by the respective ploidy level. The mean DNA content per chromosome (MC) was calculated by dividing the 2C values by the diplophasic (sporophytic) chromosome number (2n) or by dividing the 1C values by the haplophasic (gametophytic) chromosome number (n), i.e. 2C/2n or 1C/n, respectively (see Tkach et al. 2024).

Genome and chromosome size variation in the study group Poodae

2C values. Representatives of the supertribe Poodae, including the tribes Aveneae, Festuceae, Poeae and the intertribe hybrids, had 2C values, i.e. holoploid diplophasic or sporophytic genome sizes of the non-replicated nuclei, ranging between 1.49 pg in diploid Poa supina and 44.75 pg in 16–18x Anthoxanthum amarum, respectively. All of the 214 species and 399 accessions sampled in our study fell between these minimum and maximum values, which have been found in previous studies also using FCM + PI (Mao and Huff 2012; Chumová et al. 2015). Following the genome size categories of Leitch et al. (1998), 2.3% of our studied Poodae species had “very small” genomes of ≤ 2.8 pg/2C, 31.3% had “small genomes” (≤ 7 pg/2C), while the vast majority of 49% had “medium-sized” (> 7 and < 14 pg/2C), 16.4% “large” (≥ 14 and < 35 pg/2C) and 1.4% “very large genomes” of ≥ 35 pg/2C (Tables 2, 3; Figs. 1, 2A; Online Resource 1). Compared to the rest of the subfamily Pooideae, the 2C values of the Poodae were mostly lower than those of their sister supertribe Triticodae but higher than those of the phylogenetically ‘early-diverging’ lineages of the subfamily Pooideae (see Winterfeld et al. 2024).

1Cx values. The genome size of the monoploid non-replicated Poodae chromosome sets found in this study ranged from 1.13 pg/1Cx in one of the Holcus mollis accessions to 8.30 pg/1Cx in Echinaria capitata (Tables 2, 3; Figs. 1, 2B; Online Resource 1). However, these values were exceeded by a minimum value of 0.75 pg/1Cx found in Poa supina (Mao and Huff 2012) and the maximum value of 9.19 pg/1Cx found in Anthoxanthum gracile (Chumová et al. 2015). Compared to the supertribe Triticodae, the sister lineage of the Poodae, the values were therefore not significantly different from those of the tribe Bromeae but mostly smaller than those of the Triticeae (Winterfeld et al. 2024).

Mean chromosome DNA content (MC). The calculated mean chromosomes sizes of the studied Poodae ranged from 0.16 pg in the same Holcus mollis accession to 1.16 pg in Tricholemma jahandiezii (Tables 2, 3; Figs. 1, 2C; Online Resource 1), but the values were surpassed by the minimum MC of 0.11 pg previously recorded for Poa supina and the maximum value of 1.84 pg for Anthoxanthum gracile (Mao and Huff 2012; Chumová et al. 2015). The majority of the values were between 0.2 and 0.5 pg. As in the case of the 1Cx values, the MCs of the Poodae did not differ significantly from those of the tribe Bromeae in the sister supertribe Triticodae, but clearly from those of the Triticeae with mostly significantly larger chromosome sizes (Winterfeld et al. 2024).

Tribe Aveneae and its subtribes

The 2C values in the tribe Aveneae varied between 2.48 pg (MV) in diploid Torreya pallida and 33.69 pg in 14x Helictotrichon filifolium subsp. filifolium (Tables 2, 3; Figs. 1, 2A; Online Resource 1) with a maximum value of this tribe of 44.75 pg mentioned above for 16–18x Anthoxanthum amarum, implying an approximately 18-fold variation. The majority of holoploid genome sizes was between 5 pg and 10 pg.

The monoploid genome sizes were mostly between 1.22 pg/1Cx found for Amphibromus nervosus and 8.1 pg/1Cx in Tricholemma jahandiezii, the latter value being exceede only by 9.19 pg in Anthoxanthum gracile (see above). The majority of monoploid genome sizes was 2–3 pg/1Cx (Tables 2, 3; Figs. 1, 2B; Online Resource 1).

With respect to chromosome sizes, most MCs were 0.2–0.5 pg, with the outliers of exceptionally large chromosome sizes of > 1.1 pg again in T. jahandiezii and A. gracile (Tables 2, 3; Figs. 1, 2C; Online Resource 1).

Considering only the diploid Aveneae taxa, the maximum 1Cx value of species with x = 7 was 4.98 pg/1Cx in Avena hispanica (2n = 14) (Table 2; Online Resource 1), while the diploids with x = 5 had up to 9.19 pg in Anthoxanthum gracile (2n = 10) (Chumová et al. 2015).

The tribe Aveneae comprises about 54 genera and 1022 species and has a cosmopolitan distribution with a focus outside of the tropics and subtropics, namely in the temperate climatic zones of the Earth. Representatives of eight subtribes of the Aveneae were examined, arranged in alphabetical order (Tables 1–3; Figs. 2, 3; Online Resource 1).

Agrostidinae. The genera Agrostis s.l. (including Chaetopogon, Polypogon), Calamagrostis (including Ammophila, Deyeuxia) and Gastridium were studied for this predominantly northern hemisphere subtribe, comprising a total of 22 examined species and 31 accessions. The 2C values ranged from 3.83 pg for the diploid Agrostis mediterranea (syn. Polypogon maritimus) to 24.06 pg for the polyploid Calamagrostis scabrescens. For this species, only a tetraploid chromosome number reported (see CCDB), whereas judging by the 2C value, our specimen must have a higher ploidy of probably 10–12x. The 1Cx values of Agrostidinae ranged from 1.68 pg in Agrostis schraderiana to 2.83 pg (MV) in Gastridium ventricosum, and the MC from 0.24 pg to 0.40 pg in the same species. The highest 1Cx values and MCs of the whole subtribe were found in G. phleoides and G. ventricosum with 2.72–2.82 pg/1Cx and an MC of about 0.40 pg.

Among the Agrostis species studied, A. gigantea and A. subspicata (syn. Chaetopogon fasciculatus) had the highest 1Cx values of 2.35 pg and 2.38 pg, respectively (MVs). The two studied species of the former Polypogon, a genus included in Agrostis (Röser and Tkach 2024), the diploid A. mediterranea and the tetraploid A. alopecuroides largely agreed with the majority of Agrostis species with respect to their 1Cx values (1.87–1.92 pg) and MCs (both 0.27 pg). Agrostis species have often been placed in different sections (reviewed by Saarela et al. 2017; Peterson et al. 2020), mainly based on the presence/absence and length of the palea. However, the genome size data of representatives of both groups do not differ significantly, e.g. A. rupestris (short palea) with a 1Cx value of 1.77 pg and a MC of 0.25 pg compared to A. capillaris and A. castellana (long palea) with 1.71–1.75 pg/1Cx and MCs of 0.24–0.25 pg.

Most Calamagrostis species had 1Cx values of 1.85–2.27 pg/1Cx and MCs of 0.26–0.32 pg. Thus, the overall variation of 1Cx values and chromosome sizes (MC) was moderate and the representatives of the different lineages identified in Calamagrostis by molecular phylogenetics (Peterson et al. 2022), such as C. arundinacea (Deyeuxia group, clade B1), C. epigejos and C. pseudophragmites (Epigejos group, clade B2), C. scabrescens (Orientalis group, clade C1), C. purpurea (Purpurea group, clade C2), C. canescens and C. villosa (Calamagrostis group, clade C3), did not show clear differences, considering that chromosome numbers are not known or not reliably known for all taxa.

Calamagrostis rivalis, endemic to Saxony, Germany, has been reported to be octoploid (Heine 1970, 1972; Schiebold et al. 2009 as C. pseudopurpurea), but the accession we studied (11.45 pg/2C) probably had a lower ploidy level and therefore 1Cx and MC values that are probably consistent with those of the other Calamagrostis species. The same is true for the C. scabrescens accession studied (24.06 pg/2C). This species has been reported as tetraploid (CCDB), but probably has a higher ploidy.

Previous studies using FCM + PI in Agrostis capillaris, A. gigantea, A. rupestris, Calamagrostis arundinacea, C. canescens and C. epigeios in accessions with probably the same ploidy level as our samples (Šmarda et al. 2013, 2019) found genome sizes comparable in magnitude to this study, although these values were consistently lower (7–16%), except for A. rupestris, which differed by as much as 27%, a case that needs to be reexamined. The genome size of 5.42 pg/2C for C. arundinacea, also determined by FCM + PI (Pustahija et al. 2013), was about 20% lower than our estimate, although both accessions were presumably tetraploid. However, the values recorded for A. capillaris and C. canescens (Zonneveld 2019) differ from our estimates by only 0.1–0.35%, while A. gigantea was reported to have 13.2 pg/2C instead of 9.40 pg (MV) in our study, which is 1.4 times higher, indicating that it was obtained in an accession belonging to the 6x cytotype with 2n = 42, whereas in this study the 4x cytotype with 2n = 28 was used, as verified by chromosome counting for one of our three accessions studied.

However, the 2C values of 1.1 pg and 1.5 pg reported by Bai et al. (2012) for A. gigantea, which were also determined by FCM + PI appear to be incorrect and are likely based on misidentification of the plants studied.

Anthoxanthinae. This subtribe consists only of the genus Anthoxanthum s.l. if Hierochloe is included, and its species have either x = 7 (traditional Hierochloe) and x = 5 (Anthoxanthum s.s.) as chromosome base numbers. The 2C values of the studied species ranged from 7.83 pg/2C (MV) in diploids to 25.44 pg/2C in polyploids. However, the whole range in Anthoxanthum s.l. is even higher, ranging from 5.52 pg/2C in diploid A. alpinum to 44.75 pg/2C in 16x–18x A. amarum (Chumová et al. 2015), both with x = 5.

For the x = 7 taxa, the 1Cx values found were 4.73 pg in the diploid Central European A. australe (MV) and 4.88 pg in the presumably tetraploid A. nitens, a widespread Holarctic species. The 2C value of 25.44 pg for A. monticola from Alaska suggests that this accession was hexaploid (6x) rather than octoploid (8x) as usually found in this species (see CCDB). The 1Cx value of A. monticola would thus be 4.24 pg, which fits the other x = 7 species. The MC of all these x = 7 species was 0.61–0.70 pg.

Genome sizes of Anthoxanthum species from the southern hemisphere were estimated by FCM + PI in five polyploid species (4x–12x, 2n = 28–84) from New Zealand (as Hierochloe) (Murray et al. 2005). Their 2C values ranged from 18.10 pg to 29.97 pg, the (here calculated) 1Cx values from 2.32 pg to 3.14 pg and the MCs from 0.33 pg to 0.45 pg. Monoploid genome sizes (1Cx values) and chromosomes (MC) are thus significantly smaller than in the northern hemisphere x = 7 taxa. This is most likely real and is not an artifact based on methodological issues, since the DNA C-values reported by Murray et al. (2005) always agree very well with ours when the same species have been studied in both, e.g. in Deschampsia, Koeleria (Trisetum), Pentapogon, (Dichelachne) and Poa (see below), and also in the grasses of the tribe Stipeae (see Winterfeld et al. 2024).

The perennial tetraploid Anthoxanthum odoratum, belonging to the x = 5 taxa, had a 1Cx value of 3.27 pg (MV). The MC was 0.65 pg (MV) and therefore not significantly different from that of the x = 7 taxa. For A. odoratum, 1Cx values of 3.22 pg and 3.27 pg were previously found, which were also determined by FCM (Chumová et al. 2015; Zonneveld 2019). These values agree with our results, whereas the values of 2.83 pg and 2.89 pg found by Šmarda et al. (2013, 2019) are somewhat lower. The highly polyploid perennial A. amarum (16x–18x) with a 2C value of 44.75 pg (Chumová et al. 2015) had a 1Cx value of 2.48–2.80 pg and an MC of 0.50–56 pg, which is lower than in tetraploids and diploids.

The 1Cx values of diploids based on x = 5 in the perennials A. alpinum and A. maderense averaged 2.76 pg and 3.48 pg, respectively (Chumová et al. 2015). Anthoxanthum alpinum has therefore the smallest monoploid genome found in this genus. The diploid annual A. aristatum had 3.92 pg/1Cx (MV) (Table 2), which corresponds to the previously reported 3.83 pg (Chumová et al. 2015), while the diploid annual A. gracile had 9.19 pg/1Cx (Chumová et al. 2015), the highest 1Cx value found so far in the genus.

Aveninae. A total of 15 genera, 29 species and 57 accessions of the mainly northern hemisphere subtribe Aveninae were studied. The 2C values ranged from 3.66 pg in the diploid Gaudinia fragilis (MV) to 33.69 pg in the dodecaploid (12x) Helictotrichon filifolium subsp. filifolium when both diploids and polyploids are included. The 1Cx values of the diploids ranged from 1.83 pg (MV) in G. fragilis to 4.98 pg in Avena hispanica, both annuals. Their MCs ranged from 0.26 pg to 0.71 pg, respectively. In marked contrast, the 1Cx values of the polyploid species, considering those with x = 7, ranged from 2.14 pg in the verified octoploid Acrospelion distichophyllum (syn. Trisetum distichophyllum) to 8.10 pg in the tetraploid Tricholemma jahandiezii, a narrowly distributed endemic of the Moroccan Middle Atlas with an exceptionally large monoploid genome. Both are perennials.

Comparatively high 1Cx values (4.14–5.48 pg) were found in Arrhenatherum elatius (MV), Trisetopsis elongata, Sibirotrisetum sibiricum (syn. Trisetum sibiricum) and the aforementioned Avena hispanica and A. macrostachya, all perennials except for A. hispanica. Their MCs were 0.59–0.78 pg.

In the majority of the Aveninae studied (genera Graphephorum, Helictotrichon, Koeleria, Lagurus, Limnodea, Rostraria, Sphenopholis) the 1Cx values ranged from 2.15 pg/1Cx in Koeleria litvinowii to 3.52 pg/1Cx in Helictotrichon sempervirens.

Within the genera Helictotrichon and Koeleria, several species were examined. In Helictotrichon, six species and seven accessions covering the diploid to dodecaploid level, had 2C values ranging from 5.64 pg (MV) in H. sedenense subsp. sedenense to 33.69 pg in H. filifolium subsp. filifolium. The 1Cx values ranged from 2.82 pg/1Cx (MV) in H. sedenense to 3.52 pg/1Cx in H. sempervirens. The MCs were 0.40–0.50 pg. The chromosome numbers of H. aff. tianschanicum and H. tibeticum are not known, but judging from the 2C values, these species are probably tetra- and hexaploid, respectively.

A total of six species and ten accessions of the genus Koeleria were sampled, covering the ploidy levels of 2x–10x and including also K. spicata (syn. Trisetum spicatum). Chromosome numbers were counted for two accessions, taken from CCDB in the other cases, and inferred from the 2C value in the case of 3x K. vallesiana. The 2C values ranged from 5.34 pg/2C in diploid K. glauca to 22.03 pg/2C (MV) in decaploid K. pyramidata. The 1Cx values were 2.67 pg/1Cx in K. glauca and slightly lower, 2.15–2.58 pg/1Cx, in the polyploids, and the MCs were relatively uniform in all species (0.31–0.38 pg).

Our sample of the Aveninae included two species with a dysploid chromosome number, Trisetum flavescens (2n = 24) and Rostraria cristata (2n = 26) with 5.79 pg/2C and 7.43 pg/2C, respectively. Assuming that they were hypotetraploids, the 1Cx values would be about 1.45 pg and 1.86 pg, respectively, which is significantly lower than in all other Aveninae polyploids. The MCs were 0.24 pg and 0.29 pg.

The previously reported 2C values of 5.20–22.89 pg for 2x–10x taxa of Koeleria, also estimated using FCM + PI, agree with our results, as do the 1Cx values of (recalculated) 2.29–2.60 pg/1Cx (Pečinka et al. 2006). The 2C values of 5.01–5.42 pg and 8.72 pg (Zonneveld 2019) most likely refer to diploid and tetraploid Koeleria accessions, respectively. 4.06 pg/2C was recorded for diploid K. glauca, 4.43 pg/2C for a diploid K. macrantha accession, and 19.94 pg/2C for 10x K. pyramidata (Šmarda et al. 2019), which are values slightly lower than ours, as mentioned above. The 2C value of 9.92 pg estimated for tetraploid K. spicata (as Trisetum spicatum) from New Zealand (Murray et al. 2005) agrees with our result of 10.08 pg for an accession from the Tibetian Plateau.

The comparatively lew 2C values determined by FCM for other Aveninae taxa are 14.74 pg and 15.15 pg in Arrhenatherum elatius (Šmarda et al. 2013, 2019), 8.80 pg in Avena hispanica and 21.78 pg in A. macrostachya (both Yan et al. 2016), 3.44 pg in Gaudinia fragilis, 6.68 pg in Lagurus ovatus, 7.49 pg in R. cristata and 5.53 pg in Trisetum flavescens (Zonneveld 2019), which is in good agreement with our estimates, while the 4.71 pg/2C recorded for T. flavescens (Šmarda et al. 2013) is slightly lower.

Brizinae. The studied representatives of the widespread Eurasian subtribe Brizinae, excluding Macrobriza maxima (see below), had 2C values of 5.73 pg (MV) in the annual Mediterranean Briza minor (2n = 2x = 10) and 6.59 pg/2C and 13.55 pg/2C (MV), respectively, in the widespread Eurasian perennial B. media with x = 7. The former value refers to a diploid accession of B. media with 2n = 14 verified by chromosome counting from the Swiss Alps, the latter to tetraploids (2n = 4x = 28) of unknown origin. The 1Cx values were 2.87 pg (MV) in B. minor, 3.29 pg and 3.39 pg (MV) in the two cytotypes of B. media. The MCs were 0.57 pg (MV) in B. minor and 0.47–0.48 pg (MV) in B. media. Briza minor with x = 5 thus has an approximately 0.9-fold smaller monoploid genome than B. media with x = 7, but approximately 1.2-fold larger chromosomes. Previously reported 2C values were 6.68 pg, 11.92 pg and 12.38 pg for B. media (Šmarda et al. 2013, 2019; Zonneveld 2019), which obviously also refer to diploids and tetraploids, respectively. The value of 0.58 pg for B. minor (Siljak-Yakovlev et al. 2019) is most likely a calculation or typing error, as 5.8 pg would correspond to our result.

Calothecinae. Chascolytrum subaristatum with the verified chromosome number of 2n = 4x = 28 from this mainly South American subtribe had a 2C value of 8.94 pg, a 1Cx value of 2.24 pg and an MC of 0.32 pg.

Echinopogoninae. This Australasian and South American subtribe was represented by three Pentapogon species. Pentapogon crinitus and P. micranthus, both previously mostly assigned to their own genus Dichelachne, were decaploid with 2n = 10x = about 70, verified by chromosome counting, and had similar 2C values of 16.14 pg and 15.83 pg and 1Cx values of 1.61 pg and 1.58 pg, respectively, and an MC of 0.23 pg each. The octoploid Pentapogon quadrifidus var. quadrifidus (2n = 8x = about 56) had a 2C value of 14.91 pg, a 1Cx value of 1.86 pg and an MC of 0.27 pg. These values are consistent with previous genome size reports of 16.36 pg/2C in the decaploid P. crinitus (as D. crinita) and 16.85 pg/2C in the also decaploid P. micranthus (as D. micrantha) (Murray et al. 2005).

Phalaridinae. Within the monogeneric, almost cosmopolitan subtribe Phalaridinae, the three species studied had 2C values between 9.43 pg in the diploid annual P. canariensis, and 10.50 pg in the tetraploid perennial P. aquatica (MVs each). Phalaris canariensis is characterized by the dysploid monoploid chromosome number of x = 6, its 1Cx was 4.72 pg and the MC was 0.79 pg (MVs each). Phalaris aquatica and P. arundinacea, both with x = 7, had significantly lower 1Cx values of 2.63 pg (MV) and 2.46 pg and MCs of 0.38 pg (MV) and 0.35 pg, respectively. Our results are consistent with previous estimates obtained using FCM + PI, i.e. 9.61 pg/2C for P. canariensis (Zonneveld 2019), and 9.80–10.50 pg, 9.08 pg and 10.50 pg/2C for P. arundinacea (Bai et al. 2012; Šmarda et al. 2019; Zonneveld 2019).

Torreyochloinae. Both genera of this subtribe were studied, the disjunct Australasian–South American Amphibromus and the North American–East Asian Torreyochloa. The hexaploid Australian A. nervosus had a 2C value of 7.30 pg, a 1Cx value of 1.22 pg and an MC of 0.17 pg (MVs each), while the diploid American T. pallida had 2.48 pg/2C, 1.24 pg/1Cx and an MC of 0.18 pg (MVs each). The monoploid genome sizes and mean genome sizes of both taxa are thus quite similar.

Macrobriza. This genus probably originated as a hybrid taxon between a subtribe Brizinae (maternal line) and an ancestor of the subtribe Aveninae (Tkach et al. 2020). The only species is the annual Mediterranean M. maxima (syn. Briza maxima). The mean 2C value of diploid M. maxima (2n = 14) was 9.32 pg, in good agreement with a previous genome size estimate of 9.0 pg (Zonneveld 2019). The 1Cx value of M. maxima was 4.66 pg and the MC was 0.67 pg. Thus, the monoploid genome of M. maxima is approximately 1.4–1.6 times larger and the chromosomes approximately 1.2–1.4 times larger than in B. minor and B. media.

Tribe Festuceae and its subtribes

The holoploid 2C genome sizes in the studied Festuceae taxa ranged from 3.01 pg/2C in the diploid Lamarckia aurea to 20.11 pg/2C in the hexaploid Lolium giganteum (syn. Festuca gigantea). The apparently highest 2C value of 30.48 pg in Festuceae was found in 14x Festuca yvesii (Martínez-Sagarra et al. 2021). The monoploid 1Cx values varied between 1.51 pg/1Cx in Lamarckia aurea and 5.44 pg/1Cx in Festuca lachenalii (syn. Micropyrum tenellum), and the chromosome sizes (MCs) varied between 0.22 pg and 0.78 pg in the same species, respectively (Tables 2, 3; Online Resource 1). The variation of all of these quantitative genome parameters was therefore very similar to that of the tribe Aveneae, as shown in the corresponding plots (Figs. 1, 2).

The tribe Festuceae, comprising about 22 genera and 721 species (Table 1), is almost cosmopolitan, with the center of diversity in the temperate regions of the northern hemisphere, including the Mediterranean region. The tribe extends to the tropics and to the southern hemisphere along the Andes in South America and into the high mountains of Africa.

Representatives of all subtribes of the Festuceae, except of the Ammochloinae, have been studied and are listed below in alphabetical order (Tables 1–3; Figs. 2, 3; Online Resource 1).

Cynosurinae. This subtribe, which has been merged with Parapholiinae into a single subtribe based on molecular phylogenetic analyses (Rasti et al. 2023), comprises 10–11 genera, seven of which have been studied, with a total of eleven species and 41 accessions. The 2C values of this Eurasian group, which evolved mainly in drier regions from the Mediterranean to the Middle East, ranged from 5.74 pg in the diploid Desmazeria sicula (2n = 14) to 17.50 pg (MVs) in the polyploid Parapholis incurva (2n = 38).

The 2C values of all diploids (2n = 14) were only moderately variable (i.e., Catapodium rigidum, Ciliochloa effusa (syn. Cynosurus effusus), Cutandia maritima, Cynosurus cristatus, Desmazeria sicula, Falona echinata (syn. Cynosurus echinatus) and Parapholis filiformis. The minimum values were again found in Desmazeria sicula (2.87 pg/1Cx, MC of 0.41 pg), the maximum values in Falona echinata (7.77 pg/2C, 3.88 pg/1Cx, MC of 0.56 pg (MVs each).

The tetraploid Catapodium marinum (2n = 28) had a 2C value of 12.88 pg, which was about twice that of the diploids. It had a similar 1Cx value of 3.22 pg and an MC of 0.46 pg (MVs each).

Within the genus Parapholis (including Hainardia), the two euploid (orthoploid) species examined were two accessions of the diploid P. filiformis (2n = 14), and one of the tetraploid P. strigosa (2n = 28) with 2C values of 6.59 pg (MV) and 14.73 pg, 1Cx values of 3.30 pg (MV) and 3.68 pg, and MCs of 0.47 pg (MV) and 0.53 pg, respectively. In the dysploid and presumably hypotetraploid P. cylindrica (syn. H. cylindrica) with 2n = 4x = 26 and the presumably hypohexaploid P. incurva (2n = 6x = 38) the 2C values were 14.44 pg and 17.50 pg, and the MCs were 0.56 pg and 0.46 pg, respectively (MVs each). Assuming that these two dysploid species have essentially tetraploid and hexaploid chromosome complements, respectively, the approximate 1Cx values would be 3.61 pg for P. cylindrica and 2.92 pg for P. incurva.

The only taxa in Cynosurinae that have been previously studied with FCM so far appear to bey Cynosurus cristatus with 2C values of 5.38 pg, 5.43 pg, 5.94 pg and 6.10 pg (Šmarda et al. 2008, 2013, 2019; Zonneveld 2019) and P. strigosa with 13.0 pg (Zonneveld 2019). Some of these values are broadly consistent with our results, while the relatively low value of 5.38 pg represents a 1.3-fold difference from our estimate.

Dactylidinae. This small subtribe is widespread in the Old World and includes the consistently perennial genus Dactylis, which is widespread in Eurasia and the Mediterranean, and Lamarckia with the single species L. aurea, a characteristic annual of the Saharo-Sindian and Mediterranean regions. The 2C values of the Dactylidinae ranged from 3.01 pg/2C (MV) in zje diploid L. aurea to 8.52 pg/2C in the tetraploid cytotype of D. glomerata subsp. glomerata.

Dactylis was represented by accessions of diploid D. glomerata subsp. himalayensis and D. polygama and the aforementioned tetraploid D. glomerata subsp. glomerata. The diploids had holoploid genome sizes of 4.31–4.64 pg/2C (MVs), the latter slightly less than twice as much (8.52 pg/2C). The 1Cx values and MCs of both cytotypes were almost identical, i.e. 2.24 pg/1Cx versus 2.13 pg/1Cx, while the MCs were 0.32 pg versus 0.30 pg, respectively. Several previous genome size studies in Dactylis using FCM + PI, and partly recognizing narrowly defined seperate species or using taxonomic synonyms of D. glomerata, are in broad agreement with our results and recorded 2C values of 4.04–4.53pg/2C in diploids (Šmarda et al. 2008, 2019) and 7.81–9.04 pg/2C in tetraploids (Greilhuber and Baranyi 1999; Zonneveld et al. 2005; Šmarda et al. 2008, 2019; Pustahija et al. 2013; Vallès et al. 2014; Zonneveld 2019). However, slightly different and lower values have been reported for the 4x cytotype of D. glomerata without specifying the fluorescent dye (Marie and Brown 1993) and for the 2x, 4x and 6x cytotypes using DAPI (Horjales et al. 1995). In the latter case, the low estimates were most likely caused by the preferential binding of DAPI to AT base pairs, as opposed to the intercalating and not base pair-specific propidium iodide (Sumner 1990).

The second genus of the Dactylidinae, the monospecific Lamarckia with the chromosome number of 2n = 2x = 14 verified in L. aurea, had a 1Cx value of 1.51 pg (see above) and a MC of 0.22 pg (MVs each), thus a significantly smaller genome and chromosome size than D. glomerata.

Loliinae. This large subtribe, which mainly contributes to the almost worldwide distribution of the tribe Festuceae, was sampled by 17 exemplary species of the genus Festuca (including Micropyrum, Psilurus, Vulpia) and six of Lolium, comprising a total of 32 accessions.

The 2C values ranged from 3.32 pg in the diploid annual F. octoflora (syn. V. octoflora) (2n = 14) to 20.11 pg in the hexaploid perennial L. giganteum (syn. F. gigantea) (2n = 42). The 1Cx values varied between 1.66 pg in F. octoflora and 5.44 pg (MV) in F. lachenalii (syn. M. tenellum), also a diploid annual.

Otherwise, the 1Cx values showed a more or less continuous range of variation between 2.07 pg (MV) in the tetraploid F. incurva (syn. P. incurvus) (2n = 28) and 5.15 pg in the diploid L. subulatum (2n = 14), of which two accessions each were examined. These species are both annuals like F. octoflora and F. lachenalii. In contrast, the perennials have intermediate 1Cx values with also continuous variation from 2.23 pg in F. valesiaca to 4.34 pg in F. altissima and 4.85 pg in F. drymeja, all of which are diploids with 2n = 14.

Accordingly, the chromosomes (MC) were comparatively small in the annual F. octoflora (0.24 pg) and F. incurva (MV of 0.30 pg), followed by the perennial F. alpina, F. trachyphylla, F. vaginata and F. valesiaca, which had MCs of 0.32–0.35 pg. The perennials F. altissima and F. drymeja had comparatively large chromosomes (MCs of 0.62–0.69 pg), surpassed only by those of the annuals L. subulatum (MV 0.74 pg) and F. lachenalii (MV 0.78 pg).

Chromosome numbers were verified in this study for eleven Loliinae accessions including what appears to be the first chromosome count for L. subulatum (2n = 14). One of the two accessions of F. heterophylla studied is apparently hexaploid and not tetraploid as is common in this species. The new ploidy level of this accession is suggested by its 2C value, which is about 1.5 times higher than that of the other (18.13 pg/2C versus 11.38 pg/2C).

The 2C values of Festuca species extensively studied by Šmarda et al. (2008), also using FCM + PI, are mostly in good agreement with our results, e.g. 4.25–4.59 pg for F. alpina (4.76 pg in this study), 8.04 pg for F. altissima (8.68 pg in this study), 9.78 pg for F. drymeja (9.69 pg in this study), 16.39 pg for F. heteromalla (16.95 pg in this study), 11.32 pg for tetraploid F. heterophylla (11.38 pg in this study), 4.90 pg for F. vaginata (4.87 pg in this study), 16.98–17.22 pg for Lolium arundinaceum (as F. arundinacea) (16.63 pg in this study), 20.75 pg for L. giganteum (as F. gigantea) (20.11 pg in this study) and 5.51 pg for the diploid cytotype of L. perenne (5.67 pg in this study). However, the 2C values of 5.72 pg and 5.04 pg recorded for L. temulentum (Šmarda et al. 2008, 2019), possibly from the same accession, do not agree with our estimates of 7.98 pg/2C and 8.25 pg/2C for two different accessions, which also confirm a previous estimate of 8.27 pg/2C (Zonneveld 2019).

Furthermore, the 2C values of 9.15 pg for F. heterophylla (Šmarda et al. 2019), 4.02 pg for F. valesiaca (4.45 pg in this study) (Šmarda et al. 2019), 18.3 pg and 17.3 pg for L. giganteum (as F. gigantea) (Zonneveld 2019; Šmarda et al. 2019) (20.11 pg in this study), 15.59 pg, 15.94 pg, 17.45 pg and 17.3 pg for L. arundinaceum (as F. arundinacea) (Arumuganathan et al. 1999; Loureiro et al. 2007; Kopecký et al. 2010; Zonneveld 2019), 5.36 pg, 4.93 pg, 5.26 pg, 5.56 pg and 5.51 pg for diploid L. perenne (Kopecký et al. 2010; Šmarda et al. 2019; Zonneveld 2019; Frei et al. 2021 using a double-haploid plant; Moreno-Aguilar et al. 2022) and 6.4 pg for L. persicum (Moreno-Aguilar et al. 2022) (7.51 pg in this study) are broadly in agreement with our estimates.

Genome sequencing studies have reported lengths of approximately 2.26 Gbp (≈ 4.6 pg/2C), 2.467 Gbp (≈ 5.04 pg/2C) and 2.55 Gbp (≈ 5.21 pg/2C) for the Lolium perenne genome (Byrne et al. 2015; Frei et al. 2021; Nagy et al. 2022), with the more recent data closer to the value of 5.67 pg/2C in this study (see above) than the older ones, and moreover, Frei et al. (2021) also considered the genome size of 5.44 pg/2C determined by them with FCM to be more reliable than their estimate by sequencing (see above).

The above values for L. arundinaceum all refer to the hexaploid cytotype (2n = 6x = 42), which was also examined in this study. However, L. arundinaceum includes additional 4x, 8x and 10x cytotypes (Bulińska-Radomska and Lester 1986). The octo- and decaploids are often referred to as taxonomically distinct varieties or subspecies. Their 2C values were also determined by FCM + PI as 16.22 pg in the octoploid subsp. atlantigenum and 19.70 pg in the decaploid var. letourneuxianum, while the hexaploid subsp. corsicum had 16.62 pg (Ezquerro-López et al. 2017 sub Festuca). The latter agrees well with the values for the two hexaploid accessions we studied (16.54–16.72 pg/2C), although they belonged to the type subspecies/variety.

Considering the whole range of variation in holoploid genome sizes within the subtribe Loliinae, the highest known 2C values occur in dodeca- and tetradecaploid accessions of F. yvesii subspecies from the Iberian Peninsula, namely 26.69 pg and 30.40 pg (MVs calculated here), respectively (Martínez-Sagarra et. al. 2021), while the lowest value seems to be that of the aforementioned diploid F. octoflora, resulting in a total range of 3.25–29.7 Gbp, making the total variation in the Loliinae somewhat larger than previously thought (see Moreno-Aguilar et al. 2022).

Regarding the classification of Festuca and its seperate genera, it can be noted that some of the different infraspecific taxa (sections or subsections) seem to have relatively characteristic and different monoploid genome sizes: The species of F. subsect. Festuca had 1Cx values of 2.23–2.44 pg (2x F. alpina, 6x F. trachyphylla, 2x F. vaginata, 2x F. valesiaca), those of sect. Phaeochloa 4.34–4.85 pg (2x F. altissima, 2x F. drymeja) and those of sect. Aulaxyper 2.83–3.02 pg (6x F. heteromalla, 4x and 6x F. heterophylla, 6x F. rubra).

Considering the taxa often ascribed to Vulpia, the low 2C value of 3.32 pg of the diploid F. octoflora is interesting from a biogeographical and phylogenetic point of view, as this species is one of only four native American species (Soreng et al. 2000 onwards, Stace 2022) of this segregated genus. Vulpia has a center of diversity mainly in the Mediterranean, a region, where 17 of the 21 species occur (Euro + Med PlantBase 2006 onwards; Stace 2022). Compared to F. octoflora, the only American Vulpia species whose genome size has been studied so far, the diploid Old World Vulpias have 1.5–1.9 times larger genomes of about 5.11–6.27 pg/2C (see also Šmarda et al. 2008, 2019; Zonneveld 2019). Festuca octoflora (1.16 pg/1Cx) is taxonomically placed in the same section, i.e. the sect. Vulpia (Stace 2022), as 2x V. bromoides (5.12–5.86 pg/2C and 2.66–2.93 pg/1Cx), 4x V. ciliata (8.28–8.99 pg/2C and 2.06–2.25 pg/1Cx) and 6x V. myuros (12.1–13.86 pg/2C and 2.21–2.31 pg/1Cx). However, molecular phylogenetic data did not support this relationship, but showed that F. octoflora (North America and Cono Sur) and the other American Vulpias studied to date are closer to American fescues than to Old World Vulpia, revealing that traditional Vulpia is polyphyletic and most likely polytopic in origin (Inda et al. 2008; Díaz-Pérez et al. 2014; Minaya et al. 2017). This phylogenetic background is consistent with the large genome size difference between F. octoflora and the Old World Vulpias, so that at least the phylogenetically close South American 2x F. australis (syn. V. australis) may also have a small genome, possibly also the North American 6x F. microstachys (syn. V. microstachys) and other related American taxa (see clade I_FL6 of Díaz-Pérez et al. 2014). This suggests that the origin of the American F. octoflora (and its relatives?) was accompanied by a genome size reduction similar to that found in the Old World Vulpia (Šmarda et al. 2008), but even larger.

In the Old World Vulpia, it has been suggested that the origin of the hexaploids is based on allopolyploidy (Stace 2005). In particular, in the case of 6x V. myuros, an origin from a diploid species such as V. muralis and a tetraploid member of the V. ciliata-Psilurus incurvus clade has been suggested. Although the genome size of V. muralis is still unknown, that of the presumably closely related 2x V. bromoides is known to be 5.48 pg/2C, that of 4x V. ciliata 8.70 pg/2C (MV), that of 6x V. myuros 13.60 pg/2C (MV) (Šmarda et al. 2008; Zonneveld 2019) and that of 4x F. incurva (syn. Psilurus incurvus) 8.27 pg/2C. The additivity of the found genome sizes of the diploids and tetraploids (Table 5 in Online Resource 2) would be compatible with the proposed origin of the hexaploid V. myuros, with the caveat that the genome sizes of other potential parental species are not known.

Tribe Poeae and its subtribes

The 2C values ranged from 2.41 pg in the diploid Poa persica to 36.73 pg in the 12x cytotype of Arctagrostis latifolia (Tables 1–3; Figs. 2, 3; Online Resource 1). The apparently smallest 2C value recorded for Poeae to date was 1.49 pg/2C in P. supina (Mao and Huff 2012).

The 1Cx values ranged from 0.75 pg/1Cx in Poa supina, 1.21 pg/1Cx in Poa persica to 6.07/1Cx in Ventenata macra, all of which are diploids with 2n = 2x = 14. Their MCs were accordingly 0.11–0.87 pg.

The largest chromosomes known so far for the Poeae occurred in the dysploid Colpodium biebersteinianum (2n = 2x = 4) with an MC of 0.90 pg (MV), corresponding to the recorded genome sizes of 3.5–3.7 pg/2C (as Zingeria biebersteiniana), also estimated by using FCM + PI (Houben et al. 2003; Kotseruba et al. 2003, 2010).

The variation in all of these quantitative genome parameters therefore was therefore very similar to that of the tribe Aveneae, as shown in the corresponding plots (Figs. 1, 2).

The tribe Poeae comprises about 41 genera and 878 species (Table 1) and is distributed in temperate to often rather cool climates of both the northern and southern hemispheres, reaching the Arctic and Antarctic zones. Ecologically, this group appears to have a wide amplitude. It often grows in wetlands, but also occurs in forests, at high altitudes, and in relatively arid habitats.

Alopecurinae. The almost cosmopolitan Alopecurinae were represented in this study by four species of the genus Alopecurus, which comprises altogether about 44 species worldwide in temperate climates, while the small Asian, mainly Siberian to Arctic genus Limnas was not sampled. The 2C values ranged from 7.16 pg and 7.61 pg in the diploid annuals A. myosuroides and A. aequalis (both 2n = 14), respectively, to 12.73 pg (MV) in a tetraploid accession of the perennial A. pratensis (2n = 28). Alopecurus myosuroides had a 1Cx value of 3.58 pg and an MC of 0.51 pg, which were similar to those of A. pratensis with 3.18 pg/1Cx and an MC of 0.45 pg and those of A. aequalis with 3.81 pg/1Cx and an MC of 0.54 pg.

Previous FCM + PI data for Alopecurus were 7.2 pg/2C and 7.06 pg/2C for A. aequalis, 7.74 pg/2C and 7.52 pg/2C for A. myosuroides, 13.25 pg/2C and 12.6 pg/2C for A. pratensis (Wentworth et al. 2004; Zonneveld 2019), which are in agreement with our results, while those of 5.88 pg in A. aequalis and 6.58 pg in A. myosuroides (Šmarda et al. 2019) and 11.19 pg in A. pratensis (Šmarda et al. 2013) are again lower. Taxonomically, all of our studied species represent at the same time different sections of Alopecurus:

The annual A. cucullatus (syn. Cornucopiae cucullatum) had a higher 1Cx value of 4.32 pg and a higher MC of 0.62 pg (MVs) than the other studied Alopecurus species.

Although our sample of Alopecurus species is limited to four species, three different sections of this genus (Tzvelev 1976; Doğan 1999; Cabi et al. 2017; Tzvelev and Probatova 2019; Gnutikov et al. 2024) are represented: (1) sect. Pseudophalaris with diploid A. myosuroides (3.58 pg/1Cx), (2) sect. Alopecurium with diploid A. aequalis (3.81 pg/1Cx) and (3) sect. Alopecurus with tetraploid A. pratensis (3.18 pg/1Cx) and diploid A. cucullatus (4.32 pg/1Cx), a species that presumably also belongs to this section based on its placement in the trees of molecular phylogenetic analyses (Boudko 2014). The tetraploid A. pratensis has a smaller calculated monoploid genome size than all diploids of Alopecurus examined, especially with respect to the presumably closely related A. cucullatus. This may indeed reflect “genome downsizing” following polyploidization, as previously suggested for the tetraploid A. geniculatus (Wentworth et al. 2004), but molecular phylogenetic data support a possible hybrid origin of the sect. Alopecurus and the presence of different maternal lines in A. pratensis (Cabi et al. 2017; Gnutikov et al. 2024). This implies that allopolyploidy involving the donor of a small genome, rather than genome downsizing, may indeed be the case in A. pratensis (Table 5 in Online Supplement 2), which is supported by meiotic studies suggesting segmental allopolyploidy for this species (Sieber and Murray 1979; Wentworth et al. 2004).

Avenulinae. Avenula pubescens (2n = 2x = 14), the only species of this monospecific subtribe, had a comparatively large holoploid genome (10.67 pg/2C), a 1Cx value of 5.34 pg and an MC of 0.76 pg. A quite similar value of 10.1 pg/2C was found previously (Zonneveld 2019 as Helictotrichon pubescens), while 8.38 pg and 9.40 pg (Šmarda et al. 2013, 2019) again were lower.

Beckmanniinae. This small subtribe with only four genera was studied using the genera Beckmannia, with two species in the Holarctic, and the monospecific Pholiurus from western Eurasia, both characterized by a chromosome number of 2n = 2x = 14. The two Beckmannia species examined, with two accessions each of perennial B. eruciformis and the perennial to annual B. syzigachne, had fairly uniform 2C values of 6.21–6.59 pg, 1Cx values of 3.11–3.30 and MCs of 0.44–0.47 pg (MVs each). For B. eruciformis, 5.37 pg/2C has been previously reported (Šmarda et al. 2019), a value lower than ours. Pholiurus pannonicus had a larger holoploid genome than Beckmannia, with 8.14 pg/2C, a 1Cx value of 4.07 pg and an MC of 0.58 pg (MVs).

Cinninae. The subtribe Cinninae, which comprises the widely distributed Holarctic Cinna and four other genera with disjunct distributions (Gillespie et al. 2022), was represented in this study only by C. arundinacea with a verified 2n = 4x = 28, the 2C value of 12.40 pg, the 1Cx value of 3.10 pg and an MC of 0.44 pg. Three previously examined C. arundinacea accessions were found to have 10.6–10.8 pg/2C (Bai et al. 2012).

For the endemic New Zealand genus Simplicia, a southern hemisphere outlier of the Cinninae, 2C values of 11.07 pg and 10.24 pg were found for two of its three species, S. buchananii and S. laxa, respectively (Murray et al. 2005). Both are tetraploid, therefore their 1Cx values are 2.77 pg and 2.56 pg and the MCs are 0.40 pg and 0.37 pg, all in remarkable similarity to the values of the northern hemisphere Cinna.

Coleanthinae. This subtribe has an almost worldwide distribution and represents a lineage with about ten genera, of which five were studied. The 2C values ranged from 2.71 pg in the annual diploid Coleanthus subtilis to 8.80 pg (MVs) in the hexaploid Puccinellia distans and 9.19 pg in the, judging by the 2C value, also hexaploid P. leiolepis. An octoploid accession of P. maritima had a 2C value of 10.70 pg (Zonneveld 2019), the highest value recorded so far for the subtribe Coleanthinae. However, available chromosome counts indicate that up to 11-fold polyploidy occurs in the Coleanthinae (CCDB), suggesting that the maximum 2C value in this subtribe may actually be somewhat higher.

The subtribe Coleanthinae is characterized by the occurrence of three different chromosome base numbers, x = 2, 5 and 7. The presumably phylogenetically original chromosome base number of x = 7 is found in the genera Puccinellia with five sampled species and Sclerochloa with only one species (monospecific genus). The short-lived small Coleanthus subtilis had the lowest 1Cx value of 1.36 pg and an MC of 0.19 pg, followed by diploid to hexaploid, perennial Puccinellia species with 1Cx values of 1.37–1.53 pg and an MC of 0.20–0.22 pg. The six examined accessions of the diploid annual S. dura had the highest 1Cx values of 1.63 pg and an MC of 0.23 pg (MVs each).

Catabrosa aquatica, characterized by a monoploid chromosome set of x = 5, was represented by one tetraploid and one hexaploid accession, as judged by the 2C values. The 1Cx values were 1.38 and 1.28 pg, the MCs were 0.28 pg and 0.26 pg, respectively.

The two Colpodium (syn. Zingeria) species studied, the diploid C. versicolor (2n = 4) and the tetraploid C. trichopodum (2n = 8) represent the x = 2 lineage. Their 2C values were 2.85 pg and 4.98 pg. The 1Cx value of C. versicolor was 1.43 pg and its MC was 0.71 pg, while these values were not calculated for 4x C. trichopodum, an allopolyploid containing differently sized monoploid genomes (Kotseruba et al. 2003), as detailed below (see chapter “Dysploidy…”). These data are broadly consistent with a previous genome size estimate also using FCM + PI of 2.40 pg/2C in C. versicolor (Kotseruba et al. 2005). However, an estimate of 5.30 pg/2C recorded for C. trichopodum (as Z. trichopoda) (Kotseruba et al. 2003) actually refers to C. pisidica (see Kotseruba et al. 2010), a close relative of C. trichopodum that was previously not considered as separate species. In C. biebersteinianum (2n = 4), genome sizes of 3.5 pg/2C and (recalculated) 3.7 pg/2C, also determined by FCM + PI, were recorded (Kotseruba et al. 2003; Houben et al. 2003), while the hexaploid C. kochii (as Z. kochii) (2n = 12) with 6.96 pg/2C had the largest holoploid genome found so far in the x = 2 lineage (Kotseruba et al. 2010).

The previously reported DNA C-values using FCM + PI for Sclerochloa dura (3.12 pg/2C (Šmarda et al. 2008), Catabrosa aquatica (6.29 pg/2C), Puccinellia distans (8.70 pg/2C) (Zonneveld 2019) as well as P. limosa (2.59 pg/2C for the diploids of Central Germany, taxonomically treated under P. distans agg.) (Kúr et al. 2023) mostly agree well with our data, while the values recorded for Coleanthus subtilis (2.30 pg/2C), Catabrosa aquatica (5.12 pg/2C) and Sclerochloa dura (2.61 pg/2C) (Šmarda et al. 2019) are again up to 20% lower.

Hookerochloinae. Hookerochloinae comprises five genera, four of which are scattered throughout the southern hemisphere (Gillespie et al. 2022), while the genus Arctagrostis is widespread in the Holarctic and comprises only two species, one of which was sampled. Different specimens examined from a collection of A. latifolia from Alaska had 2C values of 24.51 pg and 36.73 pg. Their chromosome numbers of 2n = 56 and 2n = 84, representing the octo- and dodecaploid levels, respectively, were determined by counting. The 1Cx value of 3.06 pg and the MC of 0.44 pg were identical in both.

Miliinae. The monogeneric subtribe Miliinae has about six species in the Holarctic region, of which the perennial forest species Milium effusum, the most widespread species, was sampled. This tetraploid species (2n = 28), as verified by chromosome counting, had a 2C value of 9.23 pg, a 1Cx of 2.31 pg and an MC of 0.33 pg. The 2C value is comparable to one of the previous FCM + PI estimates, namely 8.30 pg/2C (Šmarda et al. 2019), while 5.17 pg/2C could refer to a diploid accession of M. effusum (Zonneveld 2019) or another species, as this accession is also listed as ‘M. cf. effusum’ (Zonneveld 2019: Electr. Suppl. Table 5). However, the four other estimates of 8.86–9.22 pg/2C for M. effusum (Zonneveld 2019: Electr. Suppl. Table 5) fit our result much better and should therefore actually belong to the tetraploid M. effusum.

For M. vernale, an annual diploid with the diverging dysploid chromosome number of 2n = 8, a 2C value of 6.28 pg was previously obtained (Zonneveld 2019), which largely agrees with the value of 5.73 pg previously estimated by Feulgen densitometry (Bennett and Thomas 1991). The 1Cx value of M. vernale would therefore be 3.14 pg and the MC would be 0.79 pg (Table 3).

Phleinae. The Holarctic and Andean subtribe Phleinae comprises only the genus Phleum, when its segregate genera are included. Of the approximately 15 species, nine were examined in this study, including diploid (2n = 14) to hexaploid (2n = 42) species and cytotypes, with 2C values ranging from 2.77 pg in the diploid P. cf. alpinum to 8.74 pg (MV) in the hexaploid P. pratense. The other diploids studied (P. arenarium, P. bertolonii, P. phleoides, P. rhaeticum, P. subulatum) had 3.13–4.01 pg/2C, the tetraploids P. alpinum and P. paniculatum had 6.08–6.55 pg/2C. Previous FCM + PI genome size data mostly agree well with these values, e,g. 8.1 pg/2C in presumably also 6x P. pratense (Bai et al. 2012), 2.44 pg/2C in 2x P. alpinum, 3.49 pg/2C in 4x P. phleoides and 7.63 pg–7.99 pg/2C in 6x P. pratense (Šmarda et al. 2013, 2019), 3.13 pg/2C for 2x P. arenarium and 8.47–8.78 pg/2C in 6x P. pratense (Zonneveld 2019). Several diploid accessions of P. alpinum (as P. commutatum) and P. rhaeticum had mean 2C values of 2.68 pg and 2.61 pg, respectively, while tetraploid P. alpinum accessions (as P. commutatum) from America and Europe uniformly had about 6.14–6.20 pg (Kula et al. 2006), which is also consistent with our results. The 1Cx values of all Phleum accessions examined in our study varied between 1.39 pg and 2.01 pg, the MCs between 0.20 and 0.29 pg.

The subtribe Poinae consists only of the genus Poa, into which several segregate genera have been included. Poa is the largest of all grass genera with about 570 species (Soreng et al. 2022). It is distributed almost worldwide, even reaching the Arctic region and Antarctica.

The total of 24 Poa species and 35 accessions analyzed had 2C values ranging from 2.41 pg in a probably diploid accession of P. persica (syn. Eremepoa persica) to 15.29 pg in 12x–14x P. cita. Two other diploids examined, P. chaixii and P. trivialis, had 3.15 and 3.36 pg/2C, respectively.

The tetraploids examined were the annual P. annua with 4.40 pg/2C (MV) and the perennials P. badensis with 6.01 pg/2C (MV) and P. billardierei (syn. Austrofestuca littoralis) with 7.74 pg/2C. Chromosome counts were not performed for the other species and accessions, but they all were probably polyploid. Also P. palustris with only 4.49 pg/2C (MV) was probably not diploid but tetraploid (CCDB).

The 1Cx values of the diploids ranged from 1.21 to 1.68 pg, those of the polyploids from 1.07 to 1.94, the latter in the Australasian P. billardierei. The MCs showed similar variation, ranging from 0.17 to 0.24 pg in diploids, and from 0.15 to 0.28 pg in polyploids, the latter value again in P. billardierei, indicating that this species has the largest monoploid genome and the largest chromosomes found in Poa so far.

For most of the species we studied, the 1Cx values and MCs cannot be given because the chromosome numbers of these accessions are unknown. All these species are known to have more than one cytotype (ploidy level), some show in additional aneuploidy and facultative apomixis (e.g. P. bulbosa and P. pratensis), and it is not clear which cytotypes our accessions used for genome size estimates belong to.

Our genome size data in Poa are largely consistent with the results of several previous studies also using FCM + PI, such as 4.21 pg/2C and 4.19 pg/2C (MVs) recorded for P. annua (Zonneveld 2019; Siljak-Yakovlev et al. 2020), 14.71 pg/2C (MV) for P. cita and 7.42 pg/2C for P. billardierei (as Austrofestuca littoralis) (both Murray et al. 2005), 4.2–5.8 pg/2C for P. palustris (Bai et al. 2012), and 3.32 pg/2C and 3.48 pg/2C for P. trivialis (Šmarda et al. 2008; Zonneveld 2019). For P. annua, 3.88 pg/2C (Mao and Huff 2012) and 3.87 pg/2C (Šmarda et al. 2019) have also been found, which is closer to the genome size of 1,778 Mbp (≈ 3.64 pg/2C) suggested by sequencing (Robbins et al. 2023; Benson et al. 2023) than our FCM estimate. The same discrepancy between FCM- and sequencing-based genome size estimates as in P. annua is evident in the case of P. trivialis, whose sequenced genome length of 1,350 Mbp (≈ 2.76 pg/2C) (Brunharo et al. 2024) is about 17–21% lower than the available FCM genome size estimates of 3.32–3.48 pg/2C (see above).

However, it is difficult to say which are the more accurate estimates, since sequencing approaches, although depending on the method used, typically underestimate the true genome size due to the mostly incomplete representation of the amount of repetitive DNA as has often been noted (e.g. Bennett et al. 2003; Doležel et al. 2018; Kapustová et al. 2019; Blommaert 2020; Becher et al. 2022; Winterfeld et al. 2023, 2024; Tkach et al. 2024), due to the difficulty of assembling repeats with monomers longer than the sequencing read length and the representation of two or more copies, which may be of different lengths, in only one sequence of the assembly.

Some other previously reported C-values of Poa species were also about 6–18% lower than ours, such as 2.74 pg/2C and 2.97 pg/2C instead of 3.36 pg/2C for P. trivialis (Wieners et al. 2006: p. 1537; Šmarda et al. 2013), 4.38 pg/2C instead of 5.13 pg/2C for P. angustifolia, 2. 83 pg/2C instead of 3.15 pg/2C for P. chaixii, 5.28 pg/2C instead of 6.25 pg/2C for P. nemoralis and 3.73 pg/2C instead of 4.49 pg/2C for P. palustris (Šmarda et al. 2019), while these samples, either verified by chromosome counting or most likely, have the same ploidy level as the accessions we used.

In other cases, different ploidy levels were investigated, resulting in 2.48 pg/2C for diploid (Šmarda et al. 2019) and 6.01 pg/2C for tetraploid P. badensis, and 4.08 pg/2C for tetraploid P. laxa (Šmarda et al. 2019), suggesting that our accessions of P. laxa was octoploid, judging by its genome size of 8.12 pg/2C.

The three studied accessions of P. pratensis with a genome size of 4.93–7.61 pg/2C had probably different chromosome numbers. The numerous cytotypes of this facultatively apomictic species (Bonos and Huff 2013), comprising 4x–22x ploidy levels, cause considerable variation in the size of the holoploid genomes (Eaton et al. 2004; Wieners et al. 2006; Dennhardt et al. 2016; Zonneveld 2019; Ghanbari et al. 2023; Phillips et al. 2023). Using FCM + PI, an octoploid accession of P. pratensis subsp. angustifolia was found to have 3,525.29 Mbp (≈ 7.21 pg/2C), while another accession of unknown ploidy of subsp. angustifolia had 3,248.04 Mbp (≈ 6.64 pg/2C) and of subsp. pratense had 4,030.61 Mbp (≈ 8.24 pg/2C) and 4,856.38 Mbp (≈ 9.93 pg/2C), respectively (Phillips et al. 2023).

The highest value of 18.66 pg/2C recorded so far in the genus Poa also belongs to P. pratensis (Raggi et al. 2015, using DAPI as fluorescent dye), while for most other accessions of P. pratensis have 2C values below 11 pg/2C have been recorded.

The lowest 2C values recorded in this genus refer to the perennial P. supina and the annual P. infirma, which are the diploid parental species of the aforementioned weedy annual to perennial, cosmopolitan allotetraploid P. annua (Nannfeld 1937 using the synonym P. exilis for P. infirma; Tutin 1952, 1957; Soreng et al. 2010; Mao and Huff 2012; Chen et al. 2016; Nosov et al. 2019; Benson et al. 2023).

The genome size of P. infirma was 2.52 pg/2C and 2.84 pg/2C (MVs) according to FCM data (Mao and Huff 2012; Zonneveld 2019) and was 1,125.5 Mbp (≈ 2.30 pg/2C) according to genome sequencing (Benson et al. 2023; Robbins et al. 2023). Poa supina had an even smaller genome size estimated as 1.48 pg/2C and 1.49 pg/2C by FCM (Mao and Huff 2012; Šmarda et al. 2019) and 636 Mbp (≈ 1.30 pg/2C) by DNA sequencing (Benson et al. 2023), respectively.

Unclear are some other genome size estimates for Poa species (Joshi et al. 2016), which were also performed using FCM + PI. For all eight species considered diploid (P. asiae-minoris, P. badensis, P. bucharica, P. chaixii, P. hybrida, P. pumila, P. sibirica, P. trivialis with two accessions), the identical 2C value of 2.5 pg was found, which is hardly credible.

Ventenatinae. This subtribe comprises six genera and is distributed in western Eurasia, the Mediterranean and the Middle East. Representatives of three genera were examined, all them diploid (2n = 14). The perennial Bellardiochloa violacea had the smallest holoploid genome size of 7.77 pg/2C, a 1Cx value of 3.89 pg and an MC of 0.56 pg.

Two species and three accessions of the annual genus Apera had 8.68–9.60 pg/2C, 1Cx values of 4.34–4.80 pg and MCs of 0.62–0.69 pg (A. interrupta and A. spica-venti). Previously recorded genome sizes were 8.66 pg/2C (Šmarda et al. 2019) and 10.3 pg/2C for A. spica-venti and 8.73 pg/2C for A. interrupta (both Zonneveld 2019), in agreement with our results.

The also annual Ventenata, in which two species and four accessions were studied, showed some variation, as V. dubia had 10.65 pg/2C, a 1Cx of 5.33 pg and an MC of 0.76 pg (MVs), while V. macra had a larger holoploid genome of 12.14 pg/2C, a 1Cx of 6.07 pg and an MC of 0.87 pg.

Arctopoa. This hybrid taxon of the tribe Poeae, has ancestors from the subtribes Poinae and Cinninae each (Gillespie et al. 2010, 2022; Tkach et al. 2020). The studied hexaploid Arctopoa eminens (2n = 42) had a genome size of 11.75 pg/2C and an MC of 0.28 pg. The 1Cx value of 1.96 pg and the MC of 0.28 pg are average values calculated for this allopolyploid, but the combination of very different sized monoploid genomes is also possible in this species.

Intertribe hybrid groups

The subtribes, which are taxonomically unplaced due to presumable hybrid origin or not yet assigned to a tribe, had 2C values ranging from 2.86 pg (MV) in the diploid Corynephorus canescens to 38.89 pg in 18x Helictochloa pratensis (Tables 2, 3; Figs. 1, 2A; Online Resource 1.

The largest holoploid genome size among the diploids with x = 7 was found in Mibora minima with 10.05 pg/2C (MV). In the diploid Echinaria capitata, characterized by the dysploid number of x = 9, the 2C value was even higher and amounted to 16.59 pg/1Cx (MV) (Table 2, 3; Fig. 1, 2B).

Monoploid genome sizes ranged from 1.13 pg/1Cx in a tetraploid of Holcus mollis accession to 5.03 pg/1Cx in Mibora minima, both with x = 7, exceeded by 8.30 pg/1Cx (MVs) in Echinaria capitata with x = 9. Similarly, the MCs varied between the minimum of 0.16 pg in H. mollis and the maximum of 0.72 pg in M. minima and 0.92 in E. capitata, respectively (Fig. 1, 2C).

The size distribution of 2C values, 1Cx values, and MCs of the intertribe hybrid groups as a whole closely resembles that of the tribe Aveneae (Fig. 1), which is consistent with the involvement of Aveneae as one of the parental taxa in their origin, as shown in Table 1, which updates the parental tribe designations for two subtribes compared to Tkach et al. (2020: p. 255).

The intertribe hybrid groups comprise 18 genera and approximately 159 species, representing seven subtribes, six of which were sampled in this study (Table 1). Most of their genera are distributed in the temperate regions of Eurasia and the Mediterranean, only a few are Holarctic or nearly so (Helictochloa, Scolochloa, Vahlodea), while Dryopoa is SE Australian, and only Deschampsia is nearly cosmopolitan. The subtribes of the intertribe hybrid groups are listed below in alphabetical order (Tables 1–3; Figs. 2, 3; Online Resource 1).

Airinae. This subtribe with four genera and nearly worldwide distribution had 2C values ranging from 2.86 pg in the diploid perennial Corynephorus canescens to 11.95 pg in the tetraploid perennial Avenella flexuosa (MVs each). The consistently annual Aira species studied had 2C values of 5.72 pg (MV) in A. elegans and 6.92 pg in A. praecox (MV), both of which were diploid. Tetraploid A. caryophyllea had 12.45 pg/2C (MV). The 1Cx values and MC of the Airinae species varied accordingly, with the lowest values occurring in C. canescens (1Cx value of 1.43 pg, MC of 0.20 pg) and the highest in the diploid A. praecox (1Cx value of 3.46 pg, MC of 0.49 pg). Due to its allopolyploid (amphidiploid) status (Albers 1973, 1978, 1980a, b), the 1Cx and MC were not calculated for A. caryophyllea (Table 5 in Online Resource 2).

Genome size data from most previous FCM studies were largely in agreement with our estimates and amounted to values of 6.12 pg/2C and 6.78 pg/2C for Aira praecox, 2.24 pg/2C and 3.07 pg/2C for C. canescens, 10.87 pg/2C and 12.20 pg/2C for Avenella flexuosa (as Deschampsia flexuosa) (Šmarda et al. 2019; Zonneveld 2019). Aira caryophyllea has been reported with 12.70 pg/2C (Zonneveld 2019), which agrees with our estimate, as well as the previous Feulgen-densitometric estimates of 5.87 pg for A. praecox and 12.05 pg for A. caryophyllea (Albers 1980a).

Using the non-intercalating DAPI as a fluorescent dye for FCM, the ratio between the genome sizes of A. praecox and A. caryophyllea was 0.56–0.59 pg, calculated from the data of Gregor et al. (2023), which is consistent with the 0.56 pg (MV) found in our estimates.

Aristaveninae. The genus Deschampsia, with about 62 species, is the only representative of the subtribe, which is distributed almost worldwide, including Antarctica. Deschampsia is widespread in the Holarctic, but also has a center of species diversity in South America. The 2C values varied from 7.58 pg in D. danthonioides to 18.61 pg in D. littoralis (MVs). All but one of the species studied chromosomally so far have 2n = 26 or 52 (CCDB) or slightly different chromosome numbers due to aneuploidy or B chromosomes (Albers 1972), which at first glance implies a chromosome base number of x = 13.

The only exception to x = 13 is found in D. setacea, a rare species from the comparatively humid regions of western Europe, which is diploid and has 2n = 14. It was split off at some point as the genus Aristavena. All other species with x = 7 that were occasionally listed under Deschampsia (e.g., in the CCDB), such as D. atropurpurea, D. flexuosa and D. minor actually belong to other genera, namely Avenella, Holcus and Vahlodea. However, based on molecular phylogenetic data (Tkach and Röser, unpublished data), D. setacea forms a maximally supported monophyletic group with all other Deschampsia species, making it plausible to accept its inclusion within Deschampsia. The 2C value of D. setacea was 5.25 pg (MV), the 1Cx value 2.63 pg and the MC 0.38 pg.

The Deschampsia species with 2n = 26 are either hypotetraploids, i.e. tetraploids with 2n = 28, in which two chromosomes have been lost in some way, e.g. by centric fusion of two acrocentric chromosomes, or they are allopolyploids derived from a diploid ancestor with x = 7 such as D. setacea and an unknown diploid with x = 6 (Albers 1980a, Garcia Suarez et al. 1997; Gonzales et al. 2021). Deschampsia argentea from Madeira (three accessions studied), the D. cespitosa (five accessions), D. media (one accession) and D. wibeliana (one accession specifically from the Elbe estuarine zone) from central Europe had 8.63–9.96 pg/2C, 1Cx values of about 2.16–2.49 pg when considered tetraploid and an MCs of 0.33–0.38 pg. Deschampsia koelerioides from China had a larger genome of 11.24 pg/2C, a 1Cx of 2.81 pg and an MC of 0.43 pg (MVs each).

Deschampsia littoralis from northwestern Switzerland and D. rhenana from the Lake Constance are both octoploids with 2n = 52 (CCDB). They had 18.61 and 18.30 pg/2C, 2.33 and 2.29 pg/1Cx and MCs of 0.36 and 0.35 pg, respectively (MVs for D. littoralis). The 1Cx and MC values were similar to those of the 2n = 26 species mentioned above.

The annual North American D. danthonioides has a smaller holoploid genome, 7.58 pg/2C, than the other Deschampsia species with 2n = 26. Its 1Cx value was 1.90 pg and the MC was 0.29 pg (MV each).

Previous estimates of 2C genome size using FCM in Deschampsia were 4.94 pg for D. setacea with 2n = 14 (Zonneveld 2019). Considering the taxa with 2n = 26, the 2C values were 9.51 pg for D. argentea (Greimler et al. 2022), 7.51–10.88 pg for D. cespitosa (Murray et al. 2005; Šmarda et al. 2019; Zonneveld 2019; Greimler et al. 2022 including many accessions) and 9.73–10.47 pg for D. koelerioides (Greimler et al. 2022). In the taxa with 2n = 52, the 2C values were 17.95–18.08 pg for D. littoralis and 16.96–17.72 pg for D. rhenana (Greimler et al. 2022). All these estimates are in good agreement with our data. Some variation in genome size in D. cespitosa could also be due to B chromosomes, which occur in variable numbers and sizes in this species (Albers 1972). In addition, occasional accessions of D. cespitosa with 2n = 52 have also been found, with holoploid genome sizes of 15.89–17.95 pg/2C (Greimler et al. 2022).

Helictochloinae. The genus Helictochloa, all species of which are perennial and characterized by a chromosome base number of x = 7), forms the subtribe Helictochloinae together with the dysploid Mediterranean annual Molineriella (x = 4; not studied). Helictochloa is widespread in the northern hemisphere and is characterized by a wide range of ploidy levels from 2x to 22x (e.g., Gervais 1973 as Avenochloa; Röser 1996, 1998 as Helictotrichon). The 2C values of the six studied species ranged from 7.31 pg in the diploid Helictochloa versicolor (2n = 14) to 38.89 pg in the highly polyploid H. pratensis (2n = 18x = 126). The 1Cx values varied between 3.66–4.29 pg in diploids and 2.16–3.07 in polyploids, which had correspondingly smaller chromosome sizes (an MC of 0.52–0.61 vs. 0.31–0.44 pg). For 18x H. pratensis accessions, previous estimates using FCM were 30.29–33.22 pg/2C and 35.8 pg/2C (Šmarda et al. 2019 and Zonneveld 2019 as Helictotrichon pratense), which are in the same order of magnitude as our data.

Holcinae. Both genera of this small subtribe were studied, the mainly European genus Holcus and the mainly amphi-Beringian and arctic Vahlodea. The 2C values were 3.36–7.5 pg in the two Holcus species studied and 6.32 pg (only one measurement made) in V. atropurpurea. Three accessions of the diploid H. lanatus examined had 3.36 pg/2C, 1.68 pg/1Cx, and MC of 0.24 pg (MV each). These values are consistent with 3.41 pg/2C (Zonneveld 2019), while 2.97–2.99 pg/2C are slightly lower values (Šmarda et al. 2013, 2019). A verified tetraploid H. mollis accession had 4.53 pg/2C, a 1Cx value of 1.13 pg and an MC of 0.16 pg. Another accession had 7.50 pg/2C, indicating higher polyploidy. Holcus mollis is known to be 3x–7x (CCDB), which explains why values of 5.42 pg/2C and 5.99 pg/2C were also previously found for this species (Šmarda et al. 2019; Zonneveld 2019). Vahlodea atropurpurea has been reported as diploid, but there seems to be only one chromosome available for this species (CCDB), while our accession is most likely polyploid, considering the high 2C value.

Scolochloinae. This subtribe is characterized by a remarkably disjunct distribution of its only two genera, the northern hemisphere genus Scolochloa with two species and the southeastern Australian monospecific genus Dryopoa. The tetraploid S. festucacea (2n = 28) had 9.75 pg/2C, 2.44 pg/1Cx and an MC of 0.35 pg (MVs each). The hexaploid S. marchica, a rare local endemic of eastern Germany (2n = 42) had 14.80 pg/2C, 2.47 pg/1Cx and an MC of also 0.35 pg (MVs). The genome size data suggest that S. marchica is autopolyploid and arose from S. festucacea by fusion of reduced and unreduced gametes, without the involvement of another parental taxon (Röser et al., unpubl. data).

The Australian Dryopoa dives has a much larger holoploid genome of 30.76 pg/2C. The sampled accession was verified to be decaploid (2n = 70), resulting in a comparatively high 1Cx value of 3.08 pg and an MC of 0.44 pg, consistent with the large size of the chromosomes under the microscope (not shown).

Seslerieae. This European to Mediterranean subtribe was represented in this study by all of its six genera. Five of them have a monoploid chromosome set of x = 7, namely the annual, species-poor genus Mibora and the perennial, also species-poor genera Oreochloa, Psilathera and Sesleriella as well as the perennial but species-rich genus Sesleria with about 36 species. The 2C values ranged from 6.81 pg in the diploid P. ovata to 19.87 pg in the hexaploid Sesleria comosa.

x = 7. Mibora minima, a diploid short-lived, ephemeral and winter annual species (2n = 14) had a 2C value of 10.05 pg, a 1Cx of 5.03 pg and an MC of 0.72 pg (MVs), confirming a previous estimate of 9.92 pg/2C (Zonneveld 2019). The perennial diploids (2n = 2x = 14) Oreochloa, Psilathera and Sesleriella had 9.02 pg/2C (MV), 6.81 pg/2C and 8.10 pg/2C, respectively, with 1Cx values of 4.51 pg (MV), 3.41 pg and 4.05 pg, and MCs of 0.64 pg (MV), 0.49 and 0.58 pg, respectively. The genome size of P. ovata (as Sesleria ovata) was previously reported to be 5.95 pg/2C, also determined by FCM + PI (Lazarević et al. 2015).

Interestingly, M. minima is a diminutive, short-lived annual of the winter-mild regions of Western Europe that germinates already in the fall and survives the winter as a plantlet. Its large genome size may be related to such a life form and the ecological characteristics as discussed for the ‘neotenic’ centrolepids of the family Restionaceae and other examples mentioned by Winterfeld et al. (2023).

The consistently polyploid genus Sesleria was represented by seven species and nine accessions. The four tetraploid species examined had 8.62–10.14 pg/2C, the three octoploid species 16.37–19.78 pg/2C. The values of 9.26 pg/2C, 9.78 pg/2C (MV) and 9.55 pg/2C for tetraploid S. albicans (Lysák and Doležel 1998 and Lysák et al. 2000, also using FCM + PI; Zonneveld 2019) are largely in agreement with our estimate of 10.14 pg/2C (MV). For the tetraploids S. alba and S. argentea we obtained 9.04 pg/2C (MV) and 8.62 pg/2C, which is consistent with previous estimates of 8.58 pg/2C and 8.97 pg/2C (MV), respectively (Lazarević et al. 2015). Similarly, our estimate of 18.49 pg/2C in the octoploid S. sadleriana is broadly consistent with that of 18.00 pg/2C (MV) (Lysák and Doležel 1998).

The 1Cx values of all Sesleria species examined ranged from 2.05 pg to 2.54 pg (MVs), the MC from 0.29 pg to 0.36 pg (MVs).

x = 9. The remaining genus of the subtribe Sesleriinae, the annual monospecific Echinaria with 2n = 18 has the divergent monoploid chromosome number of x = 9. Echinaria capitata had a comparatively high 2C value of 16.59 pg, a 1Cx of 8.30 pg and an MC of 0.92 pg (MVs each).

Are there any trends in the evolution of Poodae genome sizes?

Compared to the tribes Aveneae and Festuceae, the Poeae are not fundamentally different with respect to the genome size parameters (Fig. 1), but have a comparatively high proportion of taxa with low 2C values < 5 pg/2C, small monoploid genomes < 2.0 pg and show the prevalence of small chromosomes with MCs < 0.3 pg (see Figs. 1, 2, 3). This is mainly caused by the monogeneric subtribes Phleinae (Phleum) and Poinae (Poa), and most of the Coleanthinae, while one of the late-diverging lineages of the tribe Poeae has mostly large 2C values, but also large monoploid genomes (1Cx values) and large chromosomes (MCs). This lineage consists of the subtribes Alopecurinae, Beckmanniinae, Cinninae, Hookerochloinae and Ventenatinae (Fig. 3), forming the ‘ABCV clade’ (Tkach et al. 2020), which was subsequently renamed the ‘Alopecurinae superclade’ (Gillespie et al. 2022). However, this genome expansion is also seen in the monogeneric subtribe Avenulinae (Avenula), a relative of both, Phleinae/Poeae and the ABCV clade (see also Tkach et al. 2020: Fig. 7).

Regarding the tribe Festuceae, comparatively large 2C values and monoploid genome sizes and MCs are found in the subtribe Cynosurinae/Parapholiinae compared to the Dactylidinae and the Loliinae, a subtribe that apparently diverged earlier in the phylogeny. This could also imply a ‘secondary’ genome and chromosome enlargement, but the variation within Loliinae is strong and there is no clear trend (Fig. 3).

The variation of genome and chromosome sizes in the tribe Aveneae is also very striking and there seems to be no clear direction of ‘evolutionary progress’. However, the enormous variability of these parameters within the monogeneric subtribe Anthoxanthinae (Anthoxanthum) (Tables 2, 3; Figs. 2, 3) is particularly remarkable (Chumová et al. 2015, 2017, 2021). This is also true for the occurrence of the relatively small genome and chromosome sizes in the subtribe Torreyochloinae (Tables 2, 3; Figs. 2, 3), which show a surprisingly uniform monoploid genome size (1Cx value) and MC in the studied species of the diploid Torreya pallida from Canada and the hexaploid Amphibromus nervosus from Australia, which are almost maximally geographically separated.

The variability of genomic parameters appears to be associated less with long-term phylogenetic and evolutionary events and possibly more with evolutionary events within smaller groups of related taxa or individual genera. Features such as polyploidization, which per se is associated with a sudden change in genome size, but also chromosomal mutations associated with dysploid changes in chromosome number, or the evolution of different life forms (annual vs. perennial) have been discussed previously as possible factors for changes in genome size and associated traits and biological properties of organisms (Greilhuber and Leich 2013; Šmarda et al. 2019; Liddell et al. 2021; Zhan et al. 2021; Heslop-Harrison et al. 2023). The available data on numerous representatives of a relatively narrowly defined group of plants, such as the investigated subtribes grouped in the supertribe Poodae, provide good opportunities to address these questions.

Polyploidy (whole-genome duplication, WGD) and genome size

Polyploidy, the multiplication of chromosome sets by whole genome duplication (WGD) as it is commonly referred to today, represents the most significant and drastic change in holoploid genome size (2C values) because it takes effect immediately. In contrast, changes caused by a gradual increase or decrease in the proportion of certain, typically repetitive elements in the DNA are much slower. Since all angiosperms have undergone one or more cycles of genome duplication in their evolutionary past, holoploid genome sizes should in principle have become larger and larger (Leitch and Bennett 2004; Bennett and Leitch 2005; Wendel 2015; Wendel et al. 2018; X. Wang et al. 2021). However, since many angiosperms living today have very small genomes, there must inevitably be mechanisms that counteract this genome expansion through polyploidy, which is very well documented by numerous examples. Within the investigated genome sizes of grasses, there are polyploids whose holoploid genome represents the sum of the constituent individual monoploid genomes (‘additivity’) as well as those in which a reduction of the holoploid genome (‘downsizing’) has already occurred (see Table 5 in Online Resource 2 for all calculations). Both processes can occur in both autopolyploids and allopolyploids, providing new insight into the long-standing debate as to whether alloploidy promotes downsizing, whereas autoploidy is associated with genome size additivity (Ozkan et al. 2001; 2006; Soltis et al. 2003; Leitch and Bennett 2004; Bennett and Leitch 2005; Johnston et al. 2005; Garnatje et al. 2006; Suda et al. 2007; Vaio et al. 2007; Eilam et al. 2008, 2009, 2010; Leitch and Leitch 2008; Pellicer et al. 2010; Husband et al., 2013; Zenil-Ferguson et al. 2016; Becher et al. 2021; X. Wang et al. 2021; Feldman and Levy 2023b).

Additivity of monoploid genome sizes in polyploids. Polyploids whose holoploid genome sizes reflect the sum of the genome sizes of their diploid or lower polyploid relatives document a lack of or ineffective, genome size reduction after polyploidization. They can be autopolyploids or allopolyploids.

Examples found of the most likely autopolyploid taxa with little or no downsizing include (see Table 6 in Online Resource 2):

(A) triploid (3x) Koeleria vallesiana,

(B) tetraploid (4x) Anthoxanthum nitens (syn. Hierochloe nitens), Briza media (as previously noted also by Murray 1975, 1976), Catapodium marinum, Dactylis glomerata subsp. glomerata, Festuca trachyphylla, F. fasciculata (syn. Vulpia fasciculata), Gastridium ventricosum, G. phleoides, Koeleria macrantha, K. spicata (syn. Trisetum spicatum), Poa badensis and P. laxa,

(C) hexaploid (6x) Amphibromus nervosus, Festuca heteromalla, F. heterophylla, F. rubra and Scolochloa marchica,

(D) octoploid (8x) Sesleria sadleriana,

(E) hypo-tetraploid (4x-2) Deschampsia argentea, D. cespitosa, D. koelerioides, D. media and D. wibeliana and

(F) hypo-octoploid (8x-4) Deschampsia littoralis, D. rhenana in comparison with (E).

Examples of allopolyploids with little or no downsizing, characterized by an almost invariant additivity of the different parental genomes include (see Table 7 in Online Resource 2):

(G) tetraploid (4x) Aira caryophyllea, Anthoxanthum odoratum, Poa annua and

(H) hexaploid (6x) Festuca muyros (syn. Vulpia myuros).

Auto- or allopolyploids (unresolved) with little or no downsizing are (see Table 8 in Online Resource 2):

tetraploid (4x) Phleum alpinum,

(J) hexaploid (6x) Puccinellia distans and P. leiolepis,

(K) octoploid (8x) Sesleria comosa.

Polyploids with significant genome downsizing and decrease in the mean chromosome DNA content. Genome downsizing (2C and 1Cx values) and decrease of chromosome size (MC) (MC) > 10% were found in some most likely autopolyploids (Table 9 in Online Resource 2):

(L) tetraploid (4x) Koeleria litvinowii and K. pyramidata,

(M) hypo-octoploid (8x-4) Deschampsia littoralis and D. rhenana in comparison with D. setacea (2x),

(N) decaploid (10x) Helictochloa agropyroides, Koeleria pyramidata, Pentapogon crinitus and P. micranthus.

Examples of allopolyploids with significant genome downsizing and decrease of MC include (see Table 10 in Online Resource 2) are:

(O) tetraploid (4x) Alopecurus pratensis, Colpodium pisidicum/C. trichopodum (syn. Zingeria pisidica/Z. trichopoda), Holcus mollis, Phleum paniculatum,

(P) hexaploid (6x) Phleum pratense,

(Q) hypohexaploid (6x-4) Parapholis incurva,

(R) octodecaploid (18x) Helictochloa praeusta, H. pratensis subsp. pratensis.

Taxa with unresolved status of their polyploidy, whether auto- or allopolyploid, that have a significant downsizing, include (see Table 11 in Online Resource 2):

(S) tetraploid (4x) Anthoxanthum odoratum, Koeleria litvinowii,

(T) hexaploid (6x) Anthoxanthum monticola (syn. Hierochloe alpina),

(U) octoploid (8x) Sesleria tenuifolia.

Polyploids with uncertain diploid ancestors. In some cases, the genome size data help to exclude certain diploid taxa as ancestors or genome donors of some diploids (Tables 5, 12 in Online Resource 2):

The genome size of 1.66 pg/1Cx and the MC of 0.24 pg of Festuca octoflora (syn. Vulpia octoflora) suggest that this New World diploid species was not involved in the origin of the sampled Old World 4x F. fasciculata (syn. V. fasciculata), which had 3.26/1Cx and an MC of 0.47 pg, i.e. approximately twice the chromosome size of F. octoflora. Comparable size data, however, were found in the Mediterranean diploid F. alopecuros (syn. V. alopecuros), i.e. 3.14 pg/2C and an MC of 0.45 pg, thus belonging to the putative diploid ancestors of the Old World polyploids.

The highly polyploid western Mediterranean Helictotrichon filifolium subsp. filifolium (12x) had 2C, 1Cx and MC values that almost exactly matched the parameters of the diploid Helictotrichon species studied, H. decorum and H. sedenense subsp. sedenense, and could therefore considered a good example of allopolyploidy without significant genome downsizing. However, the actual genome donors have been shown to be different species, namely H. parlatorei and H. sarracenorum or related taxa (Wölk et al. 2015; Winterfeld et al. 2016), for which genome size data are not yet available.

A similar case is the allohexaploid H. sempervirens from the Western Alps, which even showed an increase in 2C and 1Cx values and MC compared to the above diploid species, but again, the relevant diploid species that acted as actual genome donors, H. parlatorei and H. setaceum or related taxa (Wölk et al. 2015; Winterfeld et al. 2016), have not been studied.

In the genus Parapholis, the sampled diploid P. filiformis apparently did not represent a genome donor for the tetraploid P. strigosa and the hypotetraploid (4x-2) P. cylindrica due to its genome size parameters with too low a 1Cx value and too low a MC.

Dysploidy and change in genome and chromosome size

Dysploidy is a less dramatic change in chromosome number than polyploidy and usually refers to one or a few chromosomes of a monoploid set of chromosomes causing a gradual change in chromosome number, typically as a decrease, termed descending or reductional dysploidy (Rieger et al. 1991; Schubert and Lysák 2011; Mandáková and Lysák 2018; Lysák 2022). It is typically associated with structural rearrangements leading to fusion of two chromosomes, usually as nested fusions, less often as end-to-end fusions, whereas gain is caused by chromosome fissions and is apparently a rarer event than descending dysploidy (Stebbins 1950; Lysák et al. 2009; Escudero et al. 2014; Lysák 2014; Carta et al. 2020; Winterfeld et al. 2020a; Mayrose and Lysák 2021; Senderowicz et al. 2021; Chase et al. 2023; Xavier et al. 2024).

Dysploidy is less common than polyploidy in the studied Poodae taxa. Of the 98 grass taxa with known chromosome number, 39 (approximately 40%) are polyploid and 59 (approximately 60%) are diploid. Dysploidy occurs in only 20 cases (approximately 20%), sometimes combined with polyploidy (Anthoxanthum, Catabrosa, Colpodium, Deschampsia, Parapholis) (Table 2; Online Resource 1). In addition, many dysploid grass taxa are annuals, supporting the hypothesis “that a low chromosome number has a selective advantage in a cross-fertilized annual species, since it increases the amount of linkage and therefore the degree of constancy of a population” (Stebbins 1950: p. 458).

Increase of 1Cx and MC. Several dysploid taxa of the grasses studied show an increase in their monoploid genome size (1Cx value) and an increase in the mean chromosome DNA content (MC) compared to their euploid relatives (for the calculations see Table 13 in Online Resource 2). The most striking example is Phalaris canariensis (x = 6), whose 1Cx and MC are increased by 363% and 214%, respectively, compared to its euploid congeners (x = 7) (Table 4; Table 13 in Online Resource 2).

Within the genus Colpodium, the diploids C. biebersteinianum and C. versicolor have 2n = 2x = 4 chromosomes. This is one of the few cases of such low chromosome number in angiosperms. Their chromosomes are 310–430% larger than those of related euploid species with x = 7 from the same subtribe Coleanthinae. The size of the monoploid genomes (1Cx values) shows less striking differences. Colpodium biebersteinianum has an increase by 23%, while C. versicolor has a decrease by 10%. This shows that chromosome fusions were the main mechanism of chromosome enlargement in these x = 2 taxa.

Echinaria capitata (2n = 2x = 18) is distinguished by a 95% increase in the 1Cx value and a 35% increase in MC compared to the other diploid but euploid species within the subtribe Sesleriinae, which have a chromosome number of x = 7. This is a notable enlargement, although less pronounced than that observed in Phalaris canariensis. It appears to be associated with a change in chromosome number from x = 7 to x = 9, which may involve chromosome fissions, but this has not been investigated. It is the only example of ascending dysploidy found among the Poodae species studied.

Decrease of 1Cx and increase of MC. A moderate decrease in monoploid genome size (1Cx value) and a moderate increase in MC of about 13–23% each were found in Briza minor (x = 5) compared to its congener B. media (x = 7) and Catabrosa aquatica (x = 5) compared to the its related taxa with x = 7 in the subtribe Coleanthinae.

Decrease of 1Cx and MC and ambiguous cases. The hypotetraploid Rostraria cristata (2n = 4x-2 = 26) shows a decrease of the 1Cx value and the MC by 31–36% compared to its diploid euploid congener R. hispida (2n = 2x = 14). However, it is not certain that this is actually caused by dysploidy, as this species is allopolyploid (Tkach, unpublished data) and may possibly also contain a smaller chromosome set than R. hispida in its tetraploid chromosome complement, causing its lowered (mean) 1Cx value and MC.

Trisetum flavescens (2n = 4x = 26) stands out for its comparatively small 1Cx and MC values, which are the smallest within the comparatively extensively sampled subtribe Aveninae (Table 2). Both values are 43–59% lower than the mean values of the diploids and tetraploids of Aveninae used for comparison (Table 4). The values would be even lower, if Tricholemma jahandiezii, with its exceptionally high and rather atypical 1Cx value and MC (chromosome size), had not been excluded from the calculation of the mean values of the tetraploid Aveninae (see Appendix to Table 13 in Online Resource 2). It would be interesting to include other cytotypes of the cytogenetically rather heterogeneous Trisetum flavescens, which also comprises hexaploids (2n = 36) (Winterfeld 2006; Winterfeld and Röser 2007b) and euploid tetraploid populations with 2n = 28 based on x = 7 (CCDB). This would also provide a more reliable means of comparing whether genome size reduction in T. flavescens actually occurred in association with dysploidy than the average genome size values from other Aveninae genera used here, or whether it occurred independently of dysploidy.

The genus Anthoxanthum, including euploid taxa with x = 7 (former Hierochloe) such as A. nitens and dysploid taxa with x = 5 such as the A. aristatum, both of which are diploids (Tables 2, 3). This appears to show a decrease in 1Cx from 4.73 pg to 3.92 pg, a 17% reduction in genome size, and an increase in chromosome size from 0.68 pg to 0.78 pg assossiated with this dysploid chromosome change. The values recorded for other diploid x = 5 taxa (A. alpinum, A. maderense) seem to show the same or even stronger decrease of the monoploid genome size (1Cx value) and in- or decrease of MCs (Chumová et al. 2015). However, the situation in Anthoxanthum is rather ambiguous, as one of the x = 5 diploids, A. gracile, has a very large genome of 9.19 pg/1Cx and an MC of 1.84 pg (Chumová et al. 2015), implying a dramatic increase. Due to the contradictory data on genome up- and down-scaling, it must be assumed that very different processes of genome evolution with very different outcomes overlap in Anthoxanthum, a conclusion supported by cytogenetic and molecular analyses (Chumová et al. 2017, 2021) (see also the following chapter).

In the genus Deschampsia, there is no clear difference between D. setacea, the only euploid and diploid species (2.63 pg/1Cx and MC of 0.38 pg), and the dysploid and at the same time polyploid taxa (2n = 4x-2 or 8x-4 and 2.16–2.81 pg/1Cx, MC of 0.33–0.43 pg). All of them are perennials, whereas D. danthonioides, the only annual species of this genus studied, has a much lower 1Cx and MC (1.90 pg/1Cx; MC 0.29 pg). As D. danthonioides also has 2n = 4x-2, its small genome size values represent rather a change related to the life form (see below).

In summary, the enlargement of genomes (1Cx values) and chromosomes (MC) associated with a dysploid change in chromosome number, as found in about half of the cases of dysploidy among the grasses studied, seems to be the most common pattern observed in angiosperms in general (Lysák et al. 2006; Cheng et al. 2013; Vaio et al. 2013; Winterfeld et al. 2018, 2020b). Such an increase in genome size has been shown to be caused by massive transposon amplification due to loss of repression and elimination of transposable elements as a result of chromosome rearrangements (Theuri et al. 2005; Lou et al. 2012; Pellicer et al. 2014; Yang et al. 2014; Rockinger et al. 2016; Ferraz et al. 2023).

Genome size reduction in the course of dysploid chromosome number change, as apparently observed in some of the studied taxa (Rostraria, Trisetum), is a pattern that has rarely been observed in other angiosperms (Chase et al. 2023).

Nevertheless, the current results seem to indicate that there is no simple causal relationship between in chromosome number changes and genome size variation in dysploidy.

Different life forms and genome size

Plants that are able to complete their life cycle in one year or less, i.e. annuals (therophytes), are typically adapted to a highly seasonal climate where there is usually a period of drought, which requires the production of seeds that can survive this hostile season. Therefore, the Mediterranean region and the Middle East, with its winter rainfall regime, is one of the most important centers for the development of annual plants, including grasses. In summary, annuals should be favored when adult mortality is high and seed persistence and seedling survival are relatively high (Hjertaas et al. 2023; Poppenwimer et al. 2023).

Ploidy and genome sizes of perennials and annuals. As a characteristic of the studied annual grasses it can be noted that they are mostly diploid and only more rarely polyploid with ploidy levels of mostly 4x and only very rarely 6x, the latter occurring among the studied taxa only in the presumably hypohexaploid Parapholis incurva (2n = 6x-4 = 38). Hexaploid annuals also are otherwise quite rare in the Poodae, but are known, for example, from a few wild annual species of Avena (oat) and of Aegilops from the Triticodae (wheat and relatives), the sister supertribe of the Poodae, while hexaploids are quite frequent among the cultivated annuals (crop species) of the tribes Aveneae and Triticeae (Rajhathy and Thomas 1974; Baum 1977; Yan et al. 2016; Feldman and Levy 2023a).

The perennial species, on the other hand, do not seem to have such restrictive constraints regarding the ploidy level, being found up to 18x in the species studied (Helictochloa pratensis) (Table 2).

2C values. The likely explanation for this striking difference between annuals and perennials seems to be that annuals have an upper limit on the 2C value, i.e. the holoploid genome size, which slows down the cell cycle by requiring the replication of a larger amount of DNA during the interphase. Although larger genome size correlates with larger cell size (nucleus/plasma ratio), which could in principle be advantageous for faster growth through fewer cell divisions, the cell cycle retardation appears to be more negative for annuals, while it may be less significant for perennials (Bennett 1972, 1987; Grant 1987; Bennett and Leitch 1995, 1997; Greilhuber and Leitch 2013).

2C values of > 20 pg were found only in perennials among the species studied (Fig. 4), namely in 21 (≈ 9.0%) of all 234 species (perennials and annuals) and 31.3% of all 167 perennial species studied (excluding facultative perennials). For the lower 2C values, which account for the majority, there is little difference between perennials and annuals, and the lowest values of < 5 pg/2C are found in both.

1Cx values. The vast majority of monoploid chromosome sets had 1–5 pg/1Cx, again with apparently little difference between perennials and annuals (Fig. 4). The comparatively few large values of > 5 pg/1Cx also occur in both, as does the largest of 8–10 pg/1Cx in the tetraploid perennial Tricholemma jahandiezii, and the diploid annuals Echinaria capitata (Table 2) and Anthoxanthum gracile (Chumová et al. 2015).

All three species have special characteristics: Tricholemma jahandiezii is a taxonomically isolated endemic of the Middle Atlas in Morocco with a comparatively small range in the highlands; Anthoxanthum gracile is a phylogenetically early-diverging species of its genus (Chumová et al. 2021) with a huge genome compared to the other species. For both taxa, an ancient relict status and a small past or present population size could be assumed, which could be responsible for the spread of genome-enlarging repetitive elements in the DNA (genetic bottleneck). Although Echinaria capitata is instead a very widespread Mediterranean species, it is characterized by a dysploid chromosome set of x = 9 as opposed to x = 7, which prevails in its close relatives of the subtribe Sesleriinae. As in some other cases in the species studied, the dysploidy and the associated chromosome rearrangements probably contributed significantly to genome enlargement in the monospecific genus Echinaria (see above Phalaris).

Mean DNA content of the chromosomes. The MCs showed a similar distribution of comparable sizes of perennials and annuals as noted for the 1Cx values. Most values were between 0.1 and 0.8 pg. Only five species had chromosomes larger than 0.8 pg. These were, in addition to the three species just mentioned, the dysploid Colpodium biebersteinianum (2n = 2x = 4) and the euploid Ventenata macra with 2n = 2x = 14, which belongs to a phylogenetic lineage that also includes some other species with comparatively large genomes (Poeae subtribes Ventenatinae and Beckmanniinae) (Tables 2, 3; Online Resource 1).

Genera with perennial and annual species. Only a few of the genera studied contain both perennial and annual species.

Briza and Macrobriza. The annual B. minor (1Cx of 2.87 pg and MC of 0.57) has a smaller monoploid genome but slightly larger chromosomes than B. media (1Cx of 3.34 pg and MC of 0.47), the only perennial of this genus studied. This opposite change in both parameters is apparently related to the dysploidy in B. minor (x = 5) compared to the euploid B. media (x = 7) and the associated chromosome restructuring.

Macrobriza maxima, a diploid euploid annual (2n = 2x = 14), differs markedly from both Briza species due to its large genome of 9.32 pg/1Cx and large chromosomes (MC of 0.67 pg). However, due to its evolutionary hybrid origin (Tkach et al. 2020), it must be taxonomically excluded from Briza and therefore cannot serve as an example of genomic changes in the course of the emergence of the therophyte life form within Briza.

Deschampsia. The only annual species of Deschampsia examined, D. danthonioides (2n = 4x-2 = 26), has a 1Cx genome size and MC about 23% lower than its also dysploid but perennial congeners with (2n = 4x-2 = 26 or 8x-4 = 52) (Table 2; Online Resource 1).

Anthoxanthum. The opposite case occurs among the diploid Anthoxanthum species, where the perennial A. alpinum has the lowest 1Cx value of 2.70 pg/1Cx and the smallest chromosomes (MC of 0.55 pg), whereas the annual A. gracile has the highest 1Cx value of 9.19 pg/1Cx and the largest chromosomes (MC of 1.8 pg) (Chumová et al. 2015). This may be related to the different processes of genome evolution mentioned above that seem to occur in this genus.

Festuca and Lolium. Among the genera Festuca and Lolium as taxonomically used in study, there is no clear distinction between annuals and perennials based on genome and chromosome sizes. The smallest 1Cx values and chromosome sizes in Festuca actually occur in the annuals, namely the diploid F. octoflora (syn. Vulpia octoflora) and the tetraploid F. incurva (syn. Psilurus incurvus) (1.66 and 2.07 pg/1Cx; MC of 0.24 and 0.30 pg), but also the highest one, in the diploid F. lachenalii (syn. Micropyrum tenellum) (5.44 pg/1Cx; MC of 0.78 pg), while the numerous perennials studied are intermediate (Table 2; Online Resource 1).

The annuals of Lolium, which are all diploid (L. persicum, L. subulatum, L. temulentum), also have larger monoploid genomes and larger chromosomes (3.76–5.15 pg/1Cx; MC 0.54–0.74 pg) than the studied perennials (L. arundinaceum, L. giganteum, L. perenne), which comprise diploid and hexaploid species (2.77–3.35 pg/1Cx; MC 0.40–0.48 pg).

These results for the genera with both annual and perennial species support the conclusion drawn above from the overall distribution of monoploid genome sizes (1Cx values) across all species studied, that the two life forms do not differ per se in this genomic trait and the associated mean chromosome sizes (MCs). Thus, the transition from a perennial to an annual life form is not necessarily associated with either genome downsizing or genome inflation, as was also observed in the genus Hordeum from the related grass tribe Triticeae (Jakob et al. 2004).

Two species in our sample were facultative annuals/perennials (winter annuals), Beckmannia syzigachne (6.59 pg/2C) and Sphenopholis obtusata (5.58 pg/2C) (Finot et al. 2004; Clayton et al. 2006 onwards). Their genome sizes were largely consistent with that of their strictly perennial congeneric taxa B. eruciformis (6.21 pg/2C) and S. intermedia (5.35 pg/2C), respectively. All species were diploid. Thus, a significantly higher genome size in obligate compared to facultative perennial monocotyledons, as suggested by Bennett (1972), is not evident from these grass examples.

The large amount of available genome size data and their partly comparatively dense taxonomic sampling allow to study also the effects of polyploidy and dysploidy in several different groups of our study group. Polyploidy as a major source of genomic variation seems to be consistently associated only in highly polyploids with genome downsizing, i.e., a reduction in genome size, whereas this is not necessarily the case in polyploids with lower valences. Furthermore, the presence or absence of downsizing can be found in both autopolyploids and allopolyploids. The same is true for dysploidy, a rarer type of genomic change in the study group, which can lead to an increase in genome size, but often also to a decrease. The origin of the strikingly low chromosome number taxa of the Poodae with only x = 2 resulted from chromosome translocations from x = 7 taxa, as suggested by the almost uniform monoploid genome sizes. The transition from a perennial to an annual life form was not associated with a consistent reduction of the genome, as indicated by the partly large monoploid genome sizes of annuals. However, there may be an upper limit to holoploid genome size (and ploidy level) in annuals that is not strongly operative in perennials, allowing the latter to show greater variability in genome size. Overall, there are apparently divergent trends in genome evolution that often overlap in Poodae taxa, making the study of genome evolution a rather surprising field of research. The widely held view that Poodae (and their sister group Triticodae) are characterized by consistently large genomes and chromosomes cannot be confirmed in any way. They are characterized by an immense variability, which makes them appear to be a group that is actually undergoing an active evolutionary unfolding.

Author Contribution

All authors contributed to the study conception and design, M.R. and N.T. collected the samples, checked the identifications, G.W. administrated the FCM analyses, all authors performed the data analysis and interpretations, M.R. led the initial writing of the manuscript, all authors participated in the writing, editing and the completion of the manuscript.

Acknowledgement

We are grateful to Laura Freisleben and Ina Reichelt (both Halle) for excellent laboratory support and for help with plant cultivation. We thank Uwe Amarell (Offenburg), Eberhard Beckemeyer (Gütersloh), Dieter Frank (Halle), Thomas Gregor (Schlitz), Kai Jensen (Hamburg), Violetta Kotseruba (St. Petersburg), Gerald Kulbrock (Gütersloh), Juraj Paule (Berlin), Uwe Raabe (Marl), Robert J. Soreng (Washington, D.C.), Peter Vogel (Karlsruhe) for valuable information, help with the plant collections and/or contribution of samples. Many botanical gardens provided seed samples (see Online Ressource 1), which we also acknowledge with gratitude. We thank Jaroslav Doležel and Jana Čížková (Institute of Experimental Botany, the Czech Academy of Sciences, Olomouc, Czech Republic) for providing reference plant standards for flow cytometry.

Ågren JA, Wright SI (2011) Co-evolution between transposable elements and their hosts: a major factor in genome size evolution? Chromosome Res 19: 777–786. doi: 10.1007/s10577-011-9229-0
Albers F (1972) Cytotaxonomie und B-Chromosomen bei Deschampsia caespitosa (L.) P.B. und verwandten Arten. Beitr Biol Pflanzen (Berlin) 48(1): 1–62.
Albers F (1973) Zwei Ausgangskaryotypen bei der Gräser-Gattung Aira L. Oesterr Bot Z 121(3–4): 251–254. doi: 10.1007/BF01373974
Albers F (1978) Beitrag zur Taxonomie, Systematik und Evolution der Subtriben Aristaveninae und Airinae (Gramineae–Aveneae). Habilitationsschrift Fachbereich Mathematik-Naturwissenschaften, Christian-Albrechts-Universität Kiel, Kiel.
Albers F (1980a) Vergleichende Karyologie der Gräser-Subtriben Aristaveninae und Airinae (Poaceae–Aveneae). Pl Syst Evol 136(3–4): 137–167. doi: 10.1007/BF01004624
Albers F (1980b) Karyogeobotanik der Gräser-Subtriben Aristaveninae und Airinae (Aveneae). Flora 169: 150–167
Anderson SN, Stitzer MC, Brohammer AB, Zhou P, Noshay JM, O’Connor CH, Hirsch CD, Ross-Ibarra J, Hirsch CN, Springer NM (2019) Transposable elements contribute to dynamic genome content in maize. Plant J 100(5): 1052–1065. doi: 10.1111/tpj.14489
Arumuganathan K, Tallury SP, Fraser ML, Bruneau AH, Qu R (1999) Nuclear DNA content of thirteen turfgrass species by flow cytometry. Crop Sci 39: 1518–1521. doi: 10.2135/cropsci1999.3951518x
Baduel P, Leduque B, Ignace A, Gy I, Gil J, Loudet O, Colot V, Quadrana L (2021) Genetic and environmental modulation of transposition shapes the evolutionary potential of Arabidopsis thaliana. Genome Biol 22: 138. doi: 10.1186/s13059-021-02348-5
Bai C, Alverson WS, Follansbee A, Waller DM (2012) New reports of nuclear DNA content for 407 vascular plant taxa from the United States. Ann Bot (Oxford) 110(8): 1623–1629. doi: 10.1093/aob/mcs222
Baker WJ, Bailey P, Barber V, Barker A, Bellot S, Bishop D, Botigué LR, Brewer G, Carruthers T, Clarkson JJ, Cook J, Cowan RS, Dodsworth S, Epitawalage N, Françoso E, Gallego B, Johnson MG, Kim JT, Leempoel K, Maurin O, Mcginnie C, Pokorny L, Roy S, Stone M, Toledo E, Wickett NJ, Zuntini AR, Eiserhardt WL, Kersey PJ, Leitch IJ, Forest F (2022) A comprehensive phylogenomic platform for exploring the angiosperm tree of life. Syst Biol 71(2): 301–319. doi: 10.1093/sysbio/syab035
Baum BR (1977) Oats: wild and cultivated. A monograph of the genus Avena L. (Poaceae). Minister of Supply and Services Canada, Ottawa.
Becher H, Powell RF, Brown MR, Metherell C, Pellicer J, Leitch IJ, Twyford AD (2021) The nature of intraspecific and interspecific genome size variation in taxonomically complex eyebrights. Ann Bot (Oxford) 128(5): 639–651. doi: 10.1093/aob/mcab102
Becher H, Sampson J, Twyford AD (2022) Measuring the invisible: the sequences causal of genome size differences in eyebrights (Euphrasia) revealed by k-mers. Frontiers Pl Sci (Online journal) 13: 818410. doi: 10.3389/fpls.2022.818410
Bennett MD (1972) Nuclear DNA content and minimum generation time in herbaceous plants. Proc R Soc Lond, B, Biol Sci 181(1063): 109–135. doi: 10.1098/rspb.1972.0042
Bennett MD (1987) Variation in genomic form in plants and its ecological implications. New Phytol 106 (suppl): 177–200. doi: 10.1111/j.1469-8137.1987.tb04689.x
Bennett MD, Leitch IJ (1995) Nuclear DNA amounts in angiosperms. Ann Bot (Oxford) 76(2):113–176. doi: 10.1006/anbo.1995.1085
Bennett MD, Leitch IJ (2005) Genome size evolution in plants. In: Gregory TR (ed) The evolution of the genome. New York: Academic Press, pp 89–162. doi: 10.1016/B978-012301463-4/50004-8
Bennett MD, Leitch IJ (1997) Nuclear DNA amounts in angiosperms – 583 new estimates. Ann Bot (Oxford) 80(2): 169–196. doi: 10.1006/anbo.1997.0415
Bennett MD, Leitch IJ, Price HJ, Johnston JS (2003) Comparisons with Caenorhabditis (approximately 100 Mb) and Drosophila (approximately 175 Mb) using flow cytometry show genome size in Arabidopsis to be approximately 157 Mb and thus approximately 25% larger than the Arabidopsis genome initiative estimate of approximately 125 Mb. Ann Bot (Oxford) 91(5): 547–557. doi: 10.1093/aob/mcg057
Bennett ST, Thomas SM (1991) Karyological analysis and genome size in Milium (Gramineae) with special reference to polyploidy and chromosomal evolution. Genome 34(6): 868–878. doi: 10.1139/g91-134
Benson CW, Sheltra MR, Maughan PJ, Jellen EN, Robbins MD, Bushman BS, Patterson EL, Hall ND, Huf DR (2023) Homoeologous evolution of the allotetraploid genome of Poa annua L. B M C Genomics 24(1): 350. doi: 10.1186/s12864-023-09456-5
Beringer M, Choudhury RR, Mandáková T, Grünig S, Leitch IJ, Lysak MA, Parisod C (2024) Biased retention of environment-responsive genes following genome fractionation. Molec Biol Evol 41(8): msae155. doi: 10.1093/molbev/msae155
Bernhardt N, Brassac J, Dong X, Willing E-M, Poskar CH, Kilian B, Blattner FR (2020) Genome-wide sequence information reveals recurrent hybridization among diploid wheat wild relatives. Plant J 102(3): 493–506. doi: 10.1111/tpj.14641
Bhadra S, Leitch IJ, Onstein RE (2023) From genome size to trait evolution during angiosperm radiation. Trends Genet 39(10): 728–735. doi: 10.1016/j.tig.2023.07.006
Blommaert J (2020) Genome size evolution: towards new model systems for old questions. Proc R Soc B Biol Sci 287: 20201441. doi:10.1098/rspb.2020.1441
Bonos SA, Huff DR (2013) Cool-season grasses: biology and breeding. In: Stier JC, Horgan BP, Bonos SA (eds) Turfgrass: biology, use, and management. Agronomy Monograph 56, American Society of Agronomy, Soil Science Society of America, Crop Science Society of America, Madison, WI, pp 590–660. doi: 10.2134/agronmonogr56.c17
Boudko E (2014) Phylogenetic analysis of subtribe Alopecurinae sensu lato (Poaceae). Master Thesis. University of Ottawa, Ottawa. doi: 10.20381/ruor-3592
Bourque G, Burns KH, Gehring M, Gorbunova V, Seluanov A, Hammell M, Imbeault M, Izsvák Z, Levin HL, Macfarlan TS, Mager DL, Feschotte C (2018) Ten things you should know about transposable elements. Genome Biol 19: 199. doi: 10.1186/s13059-018-1577-z
Brunharo CACG, Benson CW, Huff DR, Lasky JR (2024) Chromosome-scale genome assembly of Poa trivialis and population genomics reveal widespread gene flow in a cool-season grass seed production system. Plant Direct 8(3): e575. doi: 10.1002/pld3.575
Bulińska-Radomska Z, Lester RN (1986) Phylogeny of chromosome races of Festuca arundinacea and F. mairei (Poaceae) as indicated by seed protein electrophoresis. Pl Syst Evol 152(3–4): 153–166. doi: 10.1007/BF00989424
Bureš P, Elliott TL, Veselý P, Šmarda P, Forest F, Leitch IJ, Lughadha EN, Soto Gomez M, Pironon S, Brown MJM, Šmerda J, Zedek F (2024) The global distribution of angiosperm genome size is shaped by climate. New Phytol 242(2): 744–759. doi: 10.1111/nph.19544
Byrne SL, Nagy I, Pfeifer M, Armstead I, Swain S, Studer B, Mayer K, Campbell JD, Czaban A, Hentrup S, Panitz F, Bendixen C, Hedegaard J, Caccamo M, Asp T (2015) A synteny-based draft genome sequence of the forage grass Lolium perenne. Plant J 84(4): 816–826. doi: 10.1111/tpj.13037
Cabi E, Soreng RJ, Gillespie L, Boudko E (2017) Alopecurus goekyigitiana (Poaceae, subtribe Alopecurinae sensu stricto), a new species from Turkey based on morphological and molecular investigation. Turk J Bot 41(2): 8. doi: 10.3906/bot-1606–1651
Cacho NI, McIntyre PJ, Kliebenstein DJ, Strauss SY (2021) Genome size evolution is associated with climate seasonality and glucosinolates, but not life history, soil nutrients or range size, across a clade of mustards. Ann Bot (Oxford) 127(7): 887–902. doi: 10.1093/aob/mcab028
Caetano-Anollés, G (2005) Evolution of genome size in the grasses. Crop Sci (Madison) 45(5): 1809–1816. doi: 10.2135/cropsci2004.0604
Carta A, Peruzzi L (2016) Testing the large genome constraint hypothesis: plant traits, habitat and climate seasonality in Liliaceae. New Phytol 210(2): 709–716. doi: 10.1111/nph.13769
Carta A, Bedini G, Peruzzi L (2020) A deep dive into the ancestral chromosome number and genome size of flowering plants. New Phytol 228(3): 1097–1106. doi: 10.1111/nph.16668
Carta A, Mattana E, Dickie J, Vandelook F (2022) Correlated evolution of seed mass and genome size varies among life forms in flowering plants. Seed Sci Res 32: 46–52. doi: 10.1017/S0960258522000071
Catlin NS, Josephs EB (2022) The important contribution of transposable elements to phenotypic variation and evolution. Curr Opin Pl Biol 65: 102140. doi: 10.1016/j.pbi.2021.102140
CCDB (2023) The Chromosome Counts Database. Version 1.58. Available at: http://ccdb.tau.ac.il/home. Accessed 9 August 2023
Chase MW, Samuel R, Leitch AR, Guignard MS, Conran JG, Nollet F, Fletcher P, Jakob A, Cauz-Santos LA, Vignolle G, Dodsworth S, Christenhusz MJM, Buril MT, Paun O (2023) Down, then up: non-parallel genome size changes and a descending chromosome series in a recent radiation of the Australian allotetraploid plant species, Nicotiana section Suaveolentes (Solanaceae). Ann Bot (Oxford) 131(1): 123–142. doi: 10.1093/aob/mcac006
Chen S, McElroy JS, Dane F, Goertzen LR (2016), Transcriptome assembly and comparison of an allotetraploid weed species, annual bluegrass, with its two diploid progenitor species, Poa supina Schrad and Poa infirma Kunth. The Plant Genome 9:
plantgenome2015.06.0050
. doi: 10.3835/plantgenome2015.06.0050
Chen Y, Zhu X, Loukopoulos P, Weston LA, Albrecht DE, Quinn JC (2021) Genotypic identification of Panicum spp. in New South Wales, Australia using DNA barcoding. Sci Rep 11: 16055. doi: 10.1038/s41598-021-95610-6
Cheng F, Mandáková T, Wu J, Xie Q, Lysák MA, Wang X (2013) Deciphering the diploid ancestral genome of the mesohexaploid Brassica rapa. Pl Cell 25(5): 1541–1554. doi: 10.1105/tpc.113.110486
Chumová Z, Krejčíková J, Mandáková T, Suda J, Trávníček P (2015) Evolutionary and taxonomic implications of variation in nuclear genome size: lesson from the grass genus Anthoxanthum (Poaceae). PLoS ONE 10(7): e0133748. doi: 10.1371/journal.pone.0133748
Chumová Z, Záveská E, Mandáková T, Krak K, Trávníček P (2017) The Mediterranean: the cradle of Anthoxanthum (Poaceae) diploid diversity. Ann Bot (Oxford) 120(2): 285–302. doi: 10.1093/aob/mcx021
Chumová Z, Mandáková T, Trávníček P (2021) On the origin of tetraploid vernal grasses (Anthoxanthum) in Europe. Genes 12(7): 966. doi: 10.3390/genes12070966
Clayton WD, Vorontsova MS, Harman KT, Williamson H (2006 onwards) GrassBase – the online world grass flora. http://www.kew.org/data/grasses-db.html [accessed 26 October 2022].
Colonna Romano N, Fanti L (2022) Transposable elements: major players in shaping genomic and evolutionary patterns. Cells 11(6): 1048. doi: 10.3390/cells11061048
Davis J, Soreng RJ (2007) A preliminary phylogenetic analysis of the grass subfamily Pooideae subfamily Pooideae (Poaceae), with attention to structural features of the plastid and nuclear genomes, including an intron loss in GBSSI. Aliso 23(1): 335–348. doi: 10.5642/aliso.20072301.02
Dennhardt LA, DeKeyser ES, Tennefos SA, Travers SE (2016) There is no evidence of geographical patterning among invasive Kentucky bluegrass (Poa pratensis) populations in the northern great plains. Weed Sci 64(3): 409–420. doi: 10.1614/WS-D-15-00169.1
Díaz-Pérez AJ, Sharifi-Tehrani M, Inda LA, Catalán P (2014) Polyphyly, gene-duplication and extensive allopolyploidy framed the evolution of the ephemeral Vulpia grasses and other fine-leaved Loliinae (Poaceae). Molec Phylogen Evol 79: 92–105. doi: 10.1016/j.ympev.2014.06.009
Doğan M (1999) A concise taxonomic revision of the genus Alopecurus L. (Gramineae). Turk J Bot 23(4): 245–262. Available at: https://journals.tubitak.gov.tr/botany/vol23/iss4/4
Doležel J Greilhuber J, Suda J (2007) Estimation of nuclear DNA content in plants using flow cytometry. Nat Protoc 2: 2233–2244. doi: 10.1038/nprot.2007.310
Doležel J, Čížková J, Šimková H, Bartoš J (2018) One major challenge of sequencing large plant genomes is to know how big they really are. Int J Mol Sci 19(11): 3554. doi: 10.3390/ijms19113554
Doyle JJ, Coate JE (2019) Polyploidy, the nucleotype, and novelty: the impact of genome doubling on the biology of the cell. Int J Pl Sci 180(1): 1–52. doi: 10.1086/700636
Eaton T, Curley J, Williamson R, Jung G (2004) Determination of the level of variation in polyploidy among Kentucky bluegrass cultivars by means of flow cytometry. Crop Sci (Madison) 44(6): 2168–2174. doi: 10.2135/cropsci2004.2168
Ebersbach J, Muellner-Riehl AN, Michalak I, Tkach N, Hoffmann MH, Röser M, Sun H, Favre A (2017) In and out of the Qinghai-Tibet Plateau: divergence time estimation and historical biogeography of the large arctic-alpine genus Saxifraga L. J Biogeogr 44(4): 900–910. doi:10.1111/jbi.12899
Edwards EJ, Osborne CP, Strömberg CA, Smith SA, C4 Grasses Consortium, Bond WJ, Christin PA, Cousins AB, Duvall MR, Fox DL, Freckleton RP, Ghannoum O, Hartwell J, Huang Y, Janis CM, Keeley JE, Kellogg EA, Knapp AK, Leakey AD, Nelson DM, Saarela JM, Sage RF, Sala OE, Salamin N, Still CJ, Tipple B (2010) The origins of C₄ grasslands: integrating evolutionary and ecosystem science. Science 328(5978): 587–591. doi: 10.1126/science.1177216
Eilam T, Anikster Y, Millet E, Manisterski J, Feldman M (2008) Nuclear DNA amount and genome downsizing in natural and synthetic allopolyploids of the genera Aegilops and Triticum. Genome 51(8): 616–627. doi: 10.1139/G08-043
Eilam T, Anikster Y, Millet E, Manisterski J, Feldman M (2009) Genome size in natural and synthetic autopolyploids and in a natural segmental allopolyploid of several Triticeae species. Genome 52(3): 275–285. doi: 10.1139/G09-00
Eilam T, Anikster Y, Millet E, Manisterski J, Feldman M (2010) Genome size in diploids, allopolyploids, and autopolyploids of Mediterranean Triticeae. J Bot (New York) Article ID 341380. doi: 10.1155/2010/341380
Escudero M, Martín-Bravo S, Mayrose I, Fernández-Mazuecos M, Fiz-Palacios O, Hipp AL, Pimentel M, Jiménez-Mejías P, Valcárcel V, Vargas P, Luceño M (2014) Karyotypic changes through dysploidy persist longer over evolutionary time than polyploid changes. PLoS ONE 9(1): 1–7. doi: 10.1371/journal.pone.0085266
Euro + Med PlantBase (2006 onwards). Available at: http://www.emplantbase.org/home.html. Accessed 19 March 2023
Ezquerro-López D, Kopecký D, Inda LÁ (2017) Cytogenetic relationships within the Maghrebian clade of Festuca subgen. Schedonorus (Poaceae), using flow cytometry and FISH. Anal Jard Bot Madrid 74(1): 1–9. doi: 10.3989/ajbm.2455
Faizullah L, Morton JA, Hersch-Green EI, Walczyk AM, Leitch AR, Leitch IJ (2021) Exploring environmental selection on genome size in angiosperms. Trends Pl Sci 26(10): 1039–1049. doi: 10.1016/j.tplants.2021.06.001
Feldman M, Levy AA (2023a). Taxonomy and evolution of the tribe Triticeae Dumort. In: Feldman M, Levy AA (eds) Wheat evolution and domestication, Springer, Cham, Switzerland, pp 9–40. doi: 10.1007/978-3-031-30175-9_2
Feldman M, Levy AA (eds) (2023b) Wheat evolution and domestication, Springer, Cham, Switzerland. doi: 10.1007/978-3-031-30175-9
Ferraz ME, Ribeiro T, Sader M, Nascimento T, Pedrosa-Harand A (2023) Comparative analysis of repetitive DNA in dysploid and non-dysploid Phaseolus beans. Chromosome Res 31(4): 30. doi: 10.1007/s10577-023-09739-3
Finot VL, Peterson PM, Soreng RJ, Zuloaga FO (2004) A revision of Trisetum, Peyritschia, and Sphenopholis (Poaceae: Pooideae: Aveninae) in Mexico and Central America. Ann Missouri Bot Gard 91: 1–30. https://www.jstor.org/stable/3298569
Frei D, Veekman E, Grogg D, Stoffel-Studer I, Morishima A, Shimizu-Inatsugi R, Yates S, Shimizu KK, Frey JE, Studer B, Copetti D (2021) Ultralong Oxford Nanopore reads enable the development of a reference-grade perennial ryegrass genome assembly. Genome Biol Evol 13(8): evab159. doi: 10.1093/gbe/evab159
Gallaher TJ, Adams DC, Attigala L, Burke SV, Craine JM, Duvall MR, Klahs PC, Sherratt E, Wysocki WP, Clark LG (2019) Leaf shape and size track habitat transitions across forest–grassland boundaries in the grass family (Poaceae). Evolution (Lancaster) 73(5): 927–946. doi: 10.1111/evo.13722
Gallaher TJ, Peterson PM, Soreng RJ, Zuloaga FO, Li D-Z, Clark LG, Tyrrell CD, Welker CA, Kellogg EA, Teisher JK (2022) Grasses through space and time: an overview of the biogeographical and macroevolutionary history of Poaceae. J Syst Evol 60(3): 522–569. doi: 10.1111/jse.12857
Garnatje T, Garcia S, Vilatersana R, Vallès J (2006) Genome size variation in the genus Carthamus (Asteraceae, Cardueae): systematic implications and additive changes during allopolyploidization. Ann Bot (Oxford) 97(3): 461–467. doi: 10.1093/aob/mcj050
Garnatje T, Catalán P, Inda LA, Vallès J, Pyke S (2023) Genome size of grass Festuca mountain species from the southwestern European Pyrenees: variation, evolution, and new assessments. Pl Syst Evol 309: 29. doi: 10.1007/s00606-023-01867-x
Gervais C (1973) Contribution a l’etude cytologique et taxonomique des avoines vivaces. Denkschr Schweiz Naturf Ges 88: 1–166
Ghanbari MA, Salehi H, Jowkar A (2023) Genetic diversity assessment of Iranian Kentucky bluegrass accessions: II. Nuclear DNA content and its association with morphological and geographical features. Molec Biotechnol 65: 84–96. doi: 10.1007/s12033-022-00534-9
Gillespie LJ, Soreng RJ, Paradis M, Bull RD (2010) Phylogeny and reticulation in subtribe Poinae and related subtribes (Poaceae) based on nrITS, ETS, and trnTLF data. In: Seberg O, Petersen G, Barfod AS, Davids JI (eds) Diversity, phylogeny, and evolution in the monocotyledons, Aarhus University Press, Aarhus, pp 589–618
Gillespie LJ, Soreng RJ, Bull RD, de Lange PJ, Smissen RD (2022) Morphological and phylogenetic evidence for subtribe Cinninae and two new subtribes, Hookerochloinae and Dupontiinae (Poaceae tribe Poeae PPAM clade). Taxon 71(1): 52–84. doi: 10.1002/tax.12654
Gnutikov AA, Nosov NN, Punina EO, Loskutov IG, Shneyer VS, Chekrygin SA, Rodionov AV (2024) Hybridization in the subtribe Alopecurinae Dumort. (Poaceae) according to molecular phylogenetic analysis: different ploidy level tells different origin of the groups. Plants (Basel, Switzerland) 13(7): 919. doi: 10.3390/plants13070919
González ML, Chiapella JO, Urdampilleta JD (2021) The Antarctic and South American species of Deschampsia: phylogenetic relationships and cytogenetic differentiation. Syst Biodivers 19(5): 453–470. doi: 10.1080/14772000.2020.1860151
GPWG (Grass Phylogeny Working Group) (2001) Phylogeny and subfamilial classification of the grasses (Poaceae). Ann Missouri Bot Gard 88(3): 373–457. http://www.jstor.org/stable/3298585
GPWG (Grass Phylogeny Working Group) II (2012) New grass phylogeny resolves deep evolutionary relationships and discovers C₄ origins. New Phytol 193(2): 304–312. doi: 10.1111/j.1469-8137.2011.03972.x
Grant WF (1987) Genome differentiation in higher plants. In: Urbańska KM (ed) Differentiation patterns in higher plants, Academic Press, New York, pp 9–32
Gregor T, Amarell U, Berghofer M, Niederbichler C, Otto R, Paule J, Schröder CN, Mutz C (2023). Weitere Ergebnisse der Arbeitsgruppe Durchflusszytometrie: Aira, Senecio und Scrophularia. Kochia 16: 159–169. doi: 10.21248/kochia.v16.171
Greilhuber J (1995) Chromosomes of the monocotyledons (general aspects). In: Rudall PJ, Cribb PJ, Cutler DF, Humphries CJ (eds), Monocotyledons: systematics and evolution, Royal Botanic Gardens, Kew, pp 379–414
Greilhuber J, Baranyi M (1999) Feulgen densitometry: importance of a stringent hydrolysis regime. Pl Biol (Stuttgart) 1(5): 538–540. doi: 10.1111/j.1438-8677.1999.tb00780.x
Greilhuber J, Leitch IJ (2013) Genome size and the phenotype. In: Greilhuber J, Doležel J, Wendel J (eds) Plant genome diversity, vol 2. Springer, Vienna, pp 307–322. doi: 10.1007/978-3-7091-1160-4_20
Greimler J, Temsch EJ, Xue Z, Weiss–Schneeweiss H, Volkova P, Peintinger M, Wasowicz P, Shang H, Schanzer I, Chiapella JO (2022) Genome size variation in Deschampsia cespitosa sensu lato (Poaceae) in Eurasia. Pl Syst Evol 308: 9. doi: 10.1007/s00606-021-01796-7
Han T-S, Zheng Q-J, Onstein RE, Rojas-Andrés BM, Hauenschild F, Muellner-Riehl AN, Xing Y-W (2020) Polyploidy promotes species diversification of Allium through ecological shifts. New Phytol 225(1): 571–583. doi: 10.1111/nph.16098
Heine R (1970) Zur Taxonomie und Verbreitung von Calamagrostis canescens (Web.) Roth, Calamagrostis villosa (Chaix) J. F. Gmelin, Calamagrostis arundinacea (L.) Roth, Calamagrostis neglecta (Ehrh.) Pal. Beauv., Calamagrostis pseudopurpurea (Gerstl.) Heine und einiger Bastarde in Sachsen (Bezirke Dresden, Karl-Marx-Stadt und Leipzig). Unpubl. Ph.D. Thesis, Fakultät für Bau-, Wasser- und Forstwesen, TU Dresden, Dresden.
Heine R. (1972) Zur Klärung der sächsischen Calamagrostis-Art in den Muldentälern, dem Flöha- und dem Zschopautal. Feddes Repert 83(4): 275–288. doi: 10.1002/fedr.19720830406
Henniges MC, Johnston E, Pellicer J, Hidalgo O, Bennett MD, Leitch IJ (2023) The Plant DNA C-Values Database: a one-stop shop for plant genome size data. In: Garcia S, Nualart N (eds) Plant genomic and cytogenetic databases. Methods in molecular biology, vol 2703, Humana, New York, NY, pp 111–122. doi: 10.1007/978-1-0716-3389-2_9
Heslop-Harrison JS (Pat), Schwarzacher T, Liu Q (2023) Polyploidy: its consequences and enabling role in plant diversification and evolution. Ann Bot (Oxford) 131(1): 1–10. doi: 10.1093/aob/mcac132
Hjertaas AC, Preston JC, Kainulainen K, Humphreys AM, Fjellheim S (2023) Convergent evolution of the annual life history syndrome from perennial ancestors. Frontiers Pl Sci (Online journal) 13: 1048656. doi: 10.3389/fpls.2022.1048656
Hlavatá K, Záveská E, Leong-Škorničková J, Pouch M, Poulsen AD, Šída O, Khadka B, Mandáková T, Fér T (2024) Ancient hybridization and repetitive element proliferation in the evolutionary history of the monocot genus Amomum (Zingiberaceae). Frontiers Pl Sci (Online journal) 15: 1324358. doi: 10.3389/fpls.2024.1324358
Hodálová I, Mártonfiová L, Skokanová K, Majerová M, Somlyay L, Mereďa P (2020) The utility of genome size in plant identification: a case study on Sesleria (Poaceae) from Croatia and Slovenia. Plant Syst Evol 306: 87. doi: 10.1007/s00606-020-01715-2
Hoffmann MH, Röser M (2009) Taxon recruitment of the arctic flora: an analysis of phylogenies. New Phytol 182(3): 774–780. doi: 10.1111/j.1469-8137.2009.02782.x
Hoffmann MH, von Hagen KB, Hörandl E, Röser M, Tkach NV (2010) Sources of the arctic flora: origins of arctic species in Ranunculus and related genera. Int J Pl Sci 171(1): 90–106. doi: 10.1086/647918
Hoffmann MH, Schneider J, Hase P, Röser M (2013) Rapid and recent world-wide diversification of bluegrasses (Poa, Poaceae) and related genera. PLoS ONE 8(3): e60061. doi: 10.1371/journal.pone.0060061
Horjales M, Redondo N, Pérez B, Brown S (1995) Presencia en Galicia de Dactylis glomerata L. hexaploide. Bol Soc Brot 67: 223–230
Houben A, Demidov D, Gernand D, Meister A, Leach CR, Schubert I (2003) Methylation of histone H3 in euchromatin of plant chromosomes depends on basic nuclear DNA content. Plant J 33(6): 967–973. doi: 10.1046/j.1365-313X.2003.01681.x
Huang W, Zhang L, Columbus JT, Hu Y, Zhao Y, Tang L, Guo Z, Chen W, McKain M, Bartlett M, Huang CH, Li DZ, Ge S, Ma H (2022) A well-supported nuclear phylogeny of Poaceae and implications for the evolution of C₄ photosynthesis. Molec Pl 15(4): 755–777. doi: 10.1016/j.molp.2022.01.015
Husband BC, Baldwin SJ, Suda J (2013). The incidence of polyploidy in natural plant populations: major patterns and evolutionary processes. In: Greilhuber J, Doležel J, Wendel J (eds) Plant genome diversity, vol 2. Springer, Vienna, pp 255–276. https://doi.org/10.1007/978-3-7091-1160-4_16
Ibarra-Laclette E, Lyons E, Hernández-Guzmán G, Pérez-Torres CA, Carretero-Paulet L, Chang TH, Lan T, Welch AJ, Juárez MJ, Simpson J, Fernández-Cortés A, Arteaga-Vázquez M, Góngora-Castillo E, Acevedo-Hernández G, Schuster SC, Himmelbauer H, Minoche AE, Xu S, Lynch M, Oropeza-Aburto A, Cervantes-Pérez SA, de Jesús Ortega-Estrada M, Cervantes-Luevano JI, Michael TP, Mockler T, Bryant D, Herrera-Estrella A, Albert VA, Herrera-Estrella L (2013) Architecture and evolution of a minute plant genome. Nature 498(7452): 94–98. doi: 10.1038/nature12132
Inda LA, Segarra-Moragues JG, Müller J, Peterson PM, Catalán P (2008) Dated historical biogeography of the temperate Loliinae (Poaceae, Pooideae) grasses in the northern and southern hemispheres. Molec Phylogen Evol 46(3): 932–957. doi: 10.1016/j.ympev.2007.11.022
IPCN (1979 onwards) Index to plant chromosome numbers. In: Goldblatt P, Johnson DE (eds), Missouri Botanical Garden, St. Louis. Available at: http://legacy.tropicos.org/Project/IPCN. Accessed 19 August 2023
Jakob SS, Meister A, Blattner FR (2004) The considerable genome size variation of Hordeum species (Poaceae) is linked to phylogeny, life form, ecology, and speciation rates. Molec Biol Evol 21(5): 860–869. doi: 10.1093/molbev/msh092
Johnston JS, Pepper AE, Hall AE, Chen ZJ, Hodnett G, Drabek J, Lopez R, Price HJ (2005) Evolution of genome size in Brassicaceae. Ann Bot (Oxford) 95(1): 229–235. doi: 10.1093/aob/mci016
Joshi A, Bushman BS, Pickett B, Robbins MD, Staub JE, Johnson PG (2016) Phylogenetic relationships among low-ploidy species of Poa using chloroplast sequences. Genome 60(5): 384–392. doi: 10.1139/gen-2016-0110
Kadereit JW, Abbott RJ (2022) Plant speciation in the Quaternary. Plant Ecol Divers 14(3–4): 105–142. doi: 10.1080/17550874.2021.2012849
Kang M, Wang J, Huang H (2015) Nitrogen limitation as a driver of genome size evolution in a group of karst plants. Sci Rep 5: 11636. doi: 10.1038/srep11636
Kapustová V, Tulpová Z, Toegelová H, Novák P, Macas J, Karafiátová M, Hřibová E, Doležel J, Šimková H (2019) The dark matter of large cereal genomes: Long tandem repeats. Int J Mol Sci 20(10): 2483. doi: 10.3390/ijms20102483
Kellogg EA (2015) The families and genera of vascular plants, vol 13, flowering plants: monocots; poaceae. Springer, Cham, Switzerland.
Kim ES, Bolsheva NL, Samatadze TE, Nosov NN, Nosova IV, Zelenin AV, Punina EE, Muravenko OV, Rodionov AV (2009) The unique genome of two-chromosome grasses Zingeria and Colpodium, its origin, and evolution. Russ J Genet 45(11): 1329–1337. doi: 10.1134/S1022795409110076
Kong W, Wang Y, Zhang S, Yu J, Zhang X (2023) Recent advances in assembly of complex plant genomes. Genom Proteom Bioinf 21(3): 427–439. doi: 10.1016/j.gpb.2023.04.004
Kopecký D, Havránková M, Loureiro J, Castro S, Lukaszewski AJ, Bartoš J, Kopecká J, Doležel J (2010) Physical distribution of homoeologous recombination in individual chromosomes of Festuca pratensis in Lolium multiflorum. Cytogenet Genome Res 129(1–3): 162–172. doi: 10.1159/000313379
Kotseruba V, Gernand D, Meister A, Houben A (2003) Uniparental loss of ribosomal DNA in the allotetraploid grass Zingeria trichopoda (2n = 8). Genome 46: 156–163. doi: 10.1139/G02-104
Kotseruba V, Pistrick K, Gernand D, Meister A, Ghukasyan A, Gabrielyan I, Houben A (2005) Characterisation of the low-chromosome number grass Colpodium versicolor (Stev.) Schmalh. (2n = 4) by molecular cytogenetics. Caryologia 58: 241–245. doi: 10.1080/00087114.2005.10589457
Kotseruba V, Pistrick K, Blattner FR, Kumke K, Weiss O, Rutten T, Fuchs J, Endo T, Nasuda S, Ghukasyan A, Houben A (2010) The evolution of the hexaploid grass Zingeria kochii (Mez.) Tzvel. (2n = 12) was accompanied by complex hybridization and uniparental loss of ribosomal DNA. Molec Phylogen Evol 56(1): 146–155. doi: 10.1016/j.ympev.2010.01.003
Kúr P, Gregor T, Jandová M, Mesterházy A, Paule J, Píšová S, Šemberová K, Koutecký P, Ducháček M, Schneeweiss GM (2023) Cryptic invasion suggested by a cytogeographic analysis of the halophytic Puccinellia distans complex (Poaceae) in Central Europe. Frontiers Pl Sci (Online journal) 14: 1249292. doi: 10.3389/fpls.2023.1249292
Lazarević M, Kuzmanović N, Lakušić D, Alegro A, Schönswetter P, Frajman B (2015) Patterns of cytotype distribution and genome size variation in the genus Sesleria Scop. (Poaceae). Bot J Linn Soc 179(1): 126–143. doi: 10.1111/boj.12306
Lei L, Gordon SP, Liu L, Sade N, Lovell JT, del Mar Rubio-Wilhelmi M, Singan V, Sreedasyam A, Hestrin R, Phillips J, Hernandez BT, Barry K, Shu S, Jenkins J, Schmutz J, Goodstein DM, Thilmony R, Blumwald E, Vogel JP (2024) The reference genome and abiotic stress responses of the model perennial grass Brachypodium sylvaticum. G3 Genes|Genomes|Genetics 14(1): jkad245. doi: 10.1093/g3journal/jkad245
Leitch IJ, Bennett MD (2004) Genome downsizing in polyploid plants. Biol J Linn Soc 82(4): 651–663. doi: 10.1111/j.1095-8312.2004.00349.x
Leitch IJ, Bennett MD (2007) Genome size and its uses: the impact of flow cytometry. In: Doležel J, Greilhuber J, Suda J (eds) Flow cytometry with plant cells, Wiley-VCH, Weinheim, pp 153–178. doi: 10.1002/9783527610921.ch7
Leitch IJ, Chase MW, Bennett MD (1998) Phylogenetic analysis of DNA C-values provides evidence for a small ancestral genome size in flowering plants. Ann Bot (Oxford) 82 (suppl 1): 85–94. doi: 10.1006/anbo.1998.0783
Leitch IJ, Johnston E, Pellicer J, Hidalgo O, Bennett MD (2019) Plant DNA C-values Database (Release 7.1, April 2019). Available at: https://cvalues.science.kew.org/. Accessed 19 August 2023
Leitch AR, Leitch IJ (2008) Genomic plasticity and the diversity of polyploid plants. Science 320: 481–483. doi: 10.1126/science.11535
Liddell LG, Lee WG, Dale EE, Meudt HM, Matzke NJ (2021) Pioneering polyploids: the impact of whole-genome duplication on biome shifting in New Zealand Coprosma (Rubiaceae) and Veronica (Plantaginaceae). Biol Lett 17: 20210297. doi: 10.1098/rsbl.2021.0297
Loureiro J, Suda J, Doležel J, Santos C (2007) FLOWER: a plant DNA flow cytometry database. In: Doležel J, Greilhuber J, Suda J (eds) Flow cytometry with plant cells, Wiley-VCH Verlag, Weinheim, pp 423–438. doi: 10.1002/9783527610921.ch18
Loureiro J, Čertner M, Lučanová M, Sliwinska E, Kolář F, Doležel J, Garcia S, Castro S, Galbraith DW (2023) The use of flow cytometry for estimating genome sizes and DNA ploidy levels in plants. In: Heitkam T, Garcia S (eds) Plant cytogenetics and cytogenomics. Methods in molecular biology, vol 2672, Humana, New York, NY, pp 25–64. doi: 10.1007/978-1-0716-3226-0_2
Luo S, Mach J, Abramson B, Ramirez R, Schurr R, Barone P, Copenhaver G, Folkerts O (2012) The cotton centromere contains a Ty3-gypsy-like LTR retroelement. PLoS ONE 7(4): e35261. doi: 10.1371/journal.pone.0035261
Lysák MA (2014) Live and let die: centromere loss during evolution of plant chromosomes. New Phytol 203(4): 1082–1089. doi: 10.1111/nph.12885
Lysák MA (2022) Celebrating Mendel, McClintock, and Darlington: on end-to-end chromosome fusions and nested chromosome fusions. Plant Cell 34(7): 2475–2491. doi: 10.1093/plcell/koac116
Lysák MA, Doležel J (1998) Estimation of nuclear DNA content in Sesleria (Poaceae). Caryologia 52(2): 123–132
Lysák MA, Rostková A, Dixon JM, Rossi G, Doležel J (2000) Limited genome size variation in Sesleria albicans. Ann Bot (Oxford) 86(2): 399–403 doi: 10.1006/anbo.2000.1200
Lysák MA, Berr A, Pecinka A, Schmidt R, McBreen K, Schubert I (2006) Mechanisms of chromosome number reduction in Arabidopsis thaliana and related Brassicaceae species. Proc Natl Acad Sci USA 103(13): 5224–5229. doi: 10.1073/pnas.0510791103
Lysák MA, Koch AM, Beaulieu JM, Meister A, Leitch IJ. 2009. The dynamic ups and downs of genome size evolution in Brassicaceae. Molec Biol Evol 26(1): 85–98. doi: 10.1093/molbev/msn223
Mandáková T, Lysak MA (2018) Post-polyploid diploidization and diversification through dysploid changes. Curr Opin Pl Biol 42: 55–65. doi: 10.1016/j.pbi.2018.03.001
Mao Q, Huff DR (2012) The evolutionary origin of Poa annua L. Crop Sci (Madison) 52(4): 1910–1922. doi: 10.2135/cropsci2012.01.0016
Marie D, Brown, SC (1993) A cytometric exercise in plant DNA histograms, with 2C values for 70 species. Biol Cell 78(1–2): 41–51. doi: 10.1016/0248-4900(93)90113-S
Martínez-Sagarra G, Castro S, Mota L, Loureiro J, Devesa JA (2021) Genome size, chromosome number and morphological data reveal unexpected infraspecific variability in Festuca (Poaceae). Genes 12(6): 906. doi: 10.3390/genes12060906
Mayrose I, Lysák MA (2021) The evolution of chromosome numbers: mechanistic models and experimental approaches. Genome Biol Evol 13(2): evaa220. doi: 10.1093/gbe/evaa220
Mereďa P, Majerová M, Somlyay L, Pekárik L, Hodálová I (2019) Genome size variation in the Western Carpathian Sesleria (Poaceae) species. Plant Syst Evol 305: 845–864. doi: 10.1007/s00606-019-01622-1
Meudt HM, Rojas-Andrés BM, Prebble JM, Low E, Garnock-Jones PJ, Albach DC (2015) Is genome downsizing associated with diversification in polyploid lineages of Veronica? Bot J Linn Soc 178(2): 243–266. doi: 10.1111/boj.12276
Meyerson LA, Pyšek P, Lučanová M, Wigginton S, Tran C-T, Cronin JT (2020) Plant genome size influences stress tolerance of invasive and native plants via plasticity. Ecosphere 11(5): e03145. doi: 10.1002/ecs2.3145
Meyerson LA, Cronin JT, Lučanová M, Lambertini C, Brix H, Packer JG, Čuda J, Wild J, Pergl J, Pyšek P (2024) Some like it hot: small genomes may be more prevalent under climate extremes. Biol Invas 26: 1425–1436. doi: 10.1007/s10530-024-03253-1
Mhiri C, Borges F, Grandbastien M-A (2022) Specificities and dynamics of transposable elements in land plants. Biology 11(4): 488. doi: 10.3390/biology11040488
Miedaner T, Korzun V (eds) (2018) Applications of genetic and genomic research in cereals. (Woodhead publishing series in food science, technology and nutrition), Elsevier, Duxford, UK.
Minaya M, Hackel J, Namaganda M, Brochmann C, Vorontsova MS, Besnard G, Catalán P (2017) Contrasting dispersal histories of broad- and fine-leaved temperate Loliinae grasses: range expansion, founder events, and the roles of distance and barriers. J Biogeogr 44(9): 1980–1993. doi: 10.1111/jbi.13012
Moreno-Aguilar MF, Inda LA, Sánchez-Rodríguez A, Arnelas I, Catalán P (2022) Evolutionary dynamics of the repeatome explains contrasting differences in genome sizes and hybrid and polyploid origins of grass Loliinae lineages. Frontiers Pl Sci (Online journal) 13: 901733. doi: 10.3389/fpls.2022.901733
Murray BG (1975) The cytology of the genus Briza L. (Gramineae). Chromosoma 49(3): 299–308. doi: 10.1007/BF00361072
Murray BG (1976) The cytology of the genus Briza L. (Gramineae). Chromosoma 57(1): 81–93. doi: 10.1007/BF00292951
Murray BG, de Lange PJ, Ferguson AR (2005) Nuclear DNA variation, chromosome numbers and polyploidy in the endemic and indigenous grass flora of New Zealand. Ann Bot (Oxford) 96(7): 1293–1305. doi: 10.1093/aob/mci281
Nagy I, Veeckman E, Liu C, van Bel M, Vandepoele K, Jensen CS, Ruttink T, Asp T (2022) Chromosome-scale assembly and annotation of the perennial ryegrass genome. B M C Genomics 23: 505. doi: 10.1186/s12864-022-08697-0
Nannfeldt JA (1937) The chromosome numbers of Poa sect. Ochlopoa A & Gr. and their taxonomical significance. Bot Not (1937/2): 238–254. doi: https://journals.lub.lu.se/bn/article/view/11085/9891
Nosov NN, Tikhomirov VN, Machs EM, Rodionov AV (2019) On polyphyly of the former section Ochlopoa and the hybridogenic section Acroleucae (Poa, Poaceae): insights from molecular phylogenetic analyses. Nordic J Bot 37(3): e02015. doi: 10.1111/njb.02015
Novák P, Guignard MS, Neumann P, Kelly LJ, Mlinarec J, Koblížková A, Dodsworth S, Kovařík A, Pellicer J, Wang W, Macas J, Leitch IJ, Leitch AR (2020) Repeat-sequence turnover shifts fundamentally in species with large genomes. Nat Plants 6: 1325–1329. doi: 10.1038/s41477-020-00785-x
Orozco-Arias S, Isaza G, Guyot R (2019) Retrotransposons in plant genomes: structure, identification, and classification through bioinformatics and machine learning. Int J Mol Sci 20(15): 3837. doi:10.3390/ijms20153837
Orton LM, Burke SV, Duvall MR (2019) Plastome phylogenomics and characterization of rare genomic change as taxonomic markers in plastome groups 1 and 2 Poeae (Pooideae; Poaceae). PeerJ 7: e6959. doi: 10.7717/peerj.6959
Orton LM, Barberá P, Nissenbaum MP, Peterson PM, Quintanar A, Soreng RJ, Duvall MR (2021) A 313 plastome phylogenomic analysis of Pooideae: exploring relationships among the largest subfamily of grasses. Molec Phylogen Evol 159: 107110. doi: 10.1016/j.ympev.2021.107110
Ozkan H, Levy AA, Feldman M (2001) Allopolyploidy-induced rapid genome evolution in the wheat (Aegilops–Triticum) group. Plant Cell 13(8): 1735–1747. doi: 10.1105/tpc.010082.
Ozkan H, Tuna M, Galbraith DW (2006) No DNA loss in autotetraploids of Arabidopsis thaliana. Pl Breed (New York) 125(3): 288–291. doi: 10.1111/j.1439-0523.2006.01211.x
Pečinka A, Suchánková P, Lysák MA, Trávníček B, Doležel J (2006) Nuclear DNA content variation among Central European Koeleria taxa. Ann Bot (Oxford) 98: 117–122. doi: 10.1093/aob/mcl077
Pellicer J, Fay MF, Leitch IJ (2010) The largest eukaryotic genome of them all? Bot J Linn Soc 164(1): 10–15. doi: 10.1111/j.1095-8339.2010.01072.x
Pellicer J, Kelly LJ, Leitch IJ, Zomlefer WB, Fay MF (2014) A universe of dwarfs and giants: genome size and chromosome evolution in the monocot family Melanthiaceae. New Phytol 201(4): 1484–1497. https://doi.org/10.1111/nph.12617
Pellicer J, Hidalgo O, Dodsworth S, Leitch IJ (2018) Genome size diversity and its impact on the evolution of land plants. Genes 9(2): 88. doi: 10.3390/genes9020088
Pellicer J, Fernández P, Fay MF, Michálková E and Leitch IJ (2021) Genome size doubling arises from the differential repetitive DNA dynamics in the genus Heloniopsis (Melanthiaceae). Front Genet 12: 726211. doi: 10.3389/fgene.2021.726211
Peterson PM, Sylvester SP, Romaschenko K, Soreng RJ, Barberá P, Quintanar A, Aedo C (2020) A phylogeny of species near Agrostis supporting the recognition of two new genera, Agrostula and Alpagrostis (Poaceae, Pooideae, Agrostidinae) from Europe. PhytoKeys 167: 57–82. doi: 10.3897/phytokeys.167.55171
Peterson PM, Soreng RJ, Romaschenko K, Barberá P, Quintanar A, Aedo C, Saarela JM (2022) Phylogeny and biogeography of Calamagrostis (Poaceae: Pooideae: Poeae: Agrostidinae), description of a new genus, Condilorachia (Calothecinae), and expansion of Greeneochloa and Pentapogon (Echinopogoninae). J Syst Evol 60(3): 570–590. doi: 10.1111/jse.12819
Pfanzelt S, Ptáček J, Sklenář P, Hagen KB, Albach DC (2021) Genome size in South American Gentianella (Gentianaceae, Swertiinae), with a special emphasis on species from the Bolivian and Ecuadorian Andes. Ann Missouri Bot Gard 106(1): 31–46. doi: 10.3417/2020610
Phillips AR, Seetharam AS, Albert PS, AuBuchon-Elder T, Birchler JA, Buckler EW, Gillespie LJ, Hufford MB, Llaca V, Cinta Romay M, Soreng RJ, Kellogg EA, Ross-Ibarra J (2023) A happy accident: a novel turfgrass reference genome. G3 Genes|Genomes|Genetics 13(6): jkad073. doi: 10.1093/g3journal/jkad073
Pimentel M, Escudero M, Sahuquillo E, Minaya MA, Catalán P (2017) Are diversification rates and chromosome evolution in the temperate grasses (Pooideae) associated with major environmental changes in the Oligocene-Miocene? PeerJ 5: e3815. doi: 10.7717/peerj.3815
Pinto SC, Stojilković B, Zhang X, Sablowski R (2024) Plant cell size: links to cell cycle, differentiation and ploidy. Curr Opin Pl Biol 78: 102527. doi: 10.1016/j.pbi.2024.102527
Plačková K, Bureš P, Zedek F (2021) Centromere size scales with genome size across eukaryotes. Sci Rep 11: 19811. doi: 10.1038/s41598-021-99386-7
Pont C, Leroy T, Seidel M, Tondelli A, Duchemin W, Armisen D, Lang D, Bustos-Korts D, Goué N, Balfourier F, Molnár-Láng M, Lage J, Kilian B, Özkan H, Waite D, Dyer S, Letellier T, Alaux M, Wheat and Barley Legacy for Breeding Improvement (WHEALBI) Consortium, Russell J, Keller B, van Eeuwijk F, Spannagl M, Mayer KFX, Waugh R, Stein N, Cattivelli L, Haberer G, Charmet G, Salse J (2019) Tracing the ancestry of modern bread wheats. Nat Genet 51(5): 905–911. doi: 10.1038/s41588-019-0393-z
Poppenwimer T, Mayrose I, DeMalach N (2023) Revising the global biogeography of annual and perennial plants. Nature 624: 109–114. doi: 10.1038/s41586-023-06644-x
Pulido M, Casacuberta JM (2023) Transposable element evolution in plant genome ecosystems. Curr Opin Plant Biol 75: 102418. doi: 10.1016/j.pbi.2023.102418
Pustahija F, Brown SC, Bogunić F, Bašić N, Muratović E, Ollier S, Hidalgo O, Bourge M, Stevanović V, Siljak-Yakovlev S (2013) Small genomes dominate in plants growing on serpentine soils in West Balkans, an exhaustive study of 8 habitats covering 308 taxa. Pl & Soil 373(1–2): 427–453. doi: 10.1007/s11104-013-1794-x
Qiu F, Baack EJ, Whitney KD, Bock DG, Tetreault HM, Rieseberg L, Ungerer MC (2019) Phylogenetic trends and environmental correlates of nuclear genome size variation in Helianthus sunflowers. New Phytol 221: 1609–1618. doi: 10.1111/nph.15465
Quintanar A, Castroviejo S, Catalán P (2007) Phylogeny of the tribe Aveneae (Pooideae, Poaceae) inferred from plastid trnT-F and nuclear ITS sequences. Amer J Bot 94(9): 1554–1569. doi: 10.3732/ajb.94.9.1554
Raggi L, Bitocchi E, Russi L, Marconi G, Sharbel TF, Veronesi F, Albertini E (2015) Understanding genetic diversity and population structure of a Poa pratensis worldwide collection through morphological, nuclear and chloroplast diversity analysis. PLoS ONE 10(4): e0124709. doi: 10.1371/journal.pone.0124709
Rajhathy T, Thomas H (1974) Cytogenetics of oats (Avena L.). Miscellaneous Publications of the Genetics Society of Canada, Genetics Society of Canada, Ottawa.
Ramakrishnan M, Satish L, Kalendar R, Narayanan M, Kandasamy S, Sharma A, Emamverdian A, Wei Q, Zhou M (2021) The dynamism of transposon methylation for plant development and stress adaptation. Int J Mol Sci 22(21): 11387. doi: 10.3390/ijms222111387
Rasti SL, Tkach N, Röser M (2023) Disentangling conflicting molecular phylogenetic signals in nuclear and plastid DNA of the western Eurasian-Mediterranean grass genus Cynosurus and its relatives (Poaceae subtribes Cynosurinae and Parapholiinae). Preprint doi: 10.2139/ssrn.4559718
Reeves G, Francis D, Davies MS, Rogers HJ, Hodkinson TR (1998) Genome size is negatively correlated with altitude in natural populations of Dactylis glomerata. Ann Bot (Oxford) 82 (suppl 1): 99–105. doi: 10.1006/anbo.1998.0751
Rice A, Mayrose I (2023) The Chromosome Counts Database (CCDB). In: Garcia S, Nualart N (eds) Plant genomic and cytogenetic databases. Methods in molecular biology, vol 2703, Humana, New York, NY, pp 123–129. doi: 10.1007/978-1-0716-3389-2_10
Rice A, Glick L, Abadi S, Einhorn M, Kopelman NM, Salman-Minkov A, Mayzel J, Chay O, Mayrose I (2015) The Chromosome Counts Database (CCDB) – a community resource of plant chromosome numbers. New Phytol 206(1): 19–26. doi: 10.1111/nph.13191
Rieger R, Michaelis A, Green MM (1991) Glossary of genetics: classical and molecular, Springer Verlag, Berlin.
Rios EF, Kenworthy KE, Munoz PR (2015) Association of phenotypic traits with ploidy and genome size in annual ryegrass. Crop Sci (Madison) 55(5): 2078–2090.
Robbins MD, Bushman BS, Huff DR, Benson CW, Warnke SE, Maughan CA, Jellen EN, Johnson PG, Maughan PJ (2023) Chromosome-scale genome assembly and annotation of allotetraploid annual bluegrass (Poa annua L.). Genome Biol Evol 15(1): evac180. doi: 10.1093/gbe/evac180
Rockinger A, Sousa A, Carvalho FA, Renner SS (2016) Chromosome number reduction in the sister clade of Carica papaya with concomitant genome size doubling. Amer J Bot 103(6): 1082–1088. doi: 10.3732/ajb.1600134
Röser M (1996) Ecogeography of the grass genus Helictotrichon (Pooideae: Aveneae) in the Mediterranean and adjacent regions. Pl Syst Evol 203(3): 181–281. doi: 10.1007/BF00983512
Röser M (1998) Character evolution of the genus Helictotrichon (Poaceae: Aveneae) reconsidered in view of recent results in Ibero-Mauritanian and Eurasian species. Flora 193(4): 425–447. doi: 10.1016/S0367-2530(17)30869-1
Röser M, Tkach N (2024) Delimitation and nomenclature of Agrostis, Polypogon and related grasses (Poaceae subfamily Pooideae). Schlechtendalia 41: 63–67. doi: 10.25673/116223
Saarela JM, Wysocki WP, Barrett CF, Soreng RJ, Davis JI, Clark LG, Kelchner SA, Pires JC, Edger PP, Mayfield DR, Duvall MR (2015) Plastid phylogenomics of the cool-season grass subfamily: clarification of relationships among early diverging tribes. AoB Plants 7: plv046. doi: 10.1093/aobpla/plv046
Saarela JM, Bull RD, Paradis MJ, Ebata SN, Peterson PM, Soreng RJ, Paszko B (2017) Molecular phylogenetics of cool-season grasses in the subtribes Agrostidinae, Anthoxanthinae, Aveninae, Brizinae, Calothecinae, Koeleriinae and Phalaridinae (Poaceae: Pooideae: Poeae: Poeae chloroplast group 1). PhytoKeys 87: 1–139. doi: 10.3897/phytokeys.87.12774
Saarela JM, Burke SV, Wysocki WP, Barrett MD, Clark LG, Craine JM, Peterson PM, Soreng RJ, Vorontsova MS, Duvall MR (2018) A 250 plastome phylogeny of the grass family (Poaceae): Topological support under different data partitions. PeerJ 6: e4299. doi: 10.7717/peerj.4299
Schley RJ, Pellicer J, Ge X, Barrett C, Bellot S, Guignard MS, Novák P, Suda J, Fraser D, Baker WJ, Dodsworth S, Macas J, Leitch AR, Leitch IJ (2022) The ecology of palm genomes: repeat-associated genome size expansion is constrained by aridity. New Phytol 236(2): 433–446. doi: 10.1111/nph.18323
Schiebold S, Hensen I, Wesche K, Röser M (2009) Extensive clonality of the endemic Calamagrostis pseudopurpurea Gerstl. ex O. R. Heine in central Germany revealed by RAPD markers. Pl Biology (Stuttgart) 11(3): 473–482. doi: 10.1111/j.1438-8677.2008.00107.x
Schneider J, Döring E, Hilu KW, Röser M (2009) Phylogenetic structure of the grass subfamily Pooideae based on comparison of plastid matK gene–3’trnK exon and nuclear ITS sequences. Taxon 58(2): 405–424. doi: 10.1002/tax.582008
Schneider J, Winterfeld G, Röser M (2012) Polyphyly of the grass tribe Hainardieae (Poaceae: Pooideae): identification of its different lineages based on molecular phylogenetics, including morphological and cytogenetic characteristics. Org Divers Evol 12(2): 113–132. doi: 10.1007/s13127-012-0077-3
Schubert I, Lysak MA (2011) Interpretation of karyotype evolution should consider chromosome structural constraints. Trends Genet 27(6): 207–216. doi: 10.1016/j.tig.2011.03.004
Schubert M, Marcussen T, Meseguer AS, Fjellheim S (2019) The grass subfamily Pooideae: Cretaceous–Palaeocene origin and climate-driven Cenozoic diversification. Global Ecol Biogeogr 28(8): 1168–1182. doi: 10.1111/geb.12923
Senderowicz M, Nowak T, Rojek-Jelonek M, Bisaga M, Papp L, Weiss-Schneeweiss H, Kolano B (2021) Descending dysploidy and bidirectional changes in genome size accompanied Crepis (Asteraceae) evolution. Genes 12(9): 1436. doi: 10.3390/genes12091436
Serrato-Capuchina A, Matute DR (2018) The role of transposable elements in speciation. Genes 9(5), 254. doi:10.3390/genes9050254
Sieber VK, Murray BG (1979) The cytology of the genus Alopecurus (Gramineae). Bot J Linn Soc 79(4): 343–355. doi: 10.1111/j.1095-8339.1979.tb01822.x
Siljak-Yakovlev S, Farhat P, Valentin N, Bareka P, Kamari G (2019) New estimates of nuclear DNA amount for 25 taxa from Kefallinia island. Bot Chron 22: 87–108
Siljak-Yakovlev S, Lamy F, Takvorian N, Valentin N, Gouesbet V, Hennion F, Robert T (2020) Genome size and chromosome number of ten plant species from Kerguelen Islands. Polar Biol 43: 1985–1999. doi: 10.1007/s00300-020-02755-7
Sliwinska E, Loureiro J, Leitch IJ, Šmarda P, Bainard J, Bureš P, Chumová Z, Horová L, Koutecký P, Lučanová M, Trávníček P, Galbraith DW (2022) Application-based guidelines for best practices in plant flow cytometry. Cytometry 101(9): 749–781. doi: 10.1002/cyto.a.24499
Šmarda P, Bureš P (2006) Intraspecific DNA content variability in Festuca pallens on different geographical scales and ploidy levels. Ann Bot (Oxford) 98: 665–678. doi: 10.1093/aob/mcl150
Šmarda P, Bureš P, Horová L, Foggi B, Rossi G (2008) Genome size and GC content evolution of Festuca: ancestral expansion and subsequent reduction. Ann Bot (Oxford) 101(3): 421–433. doi:10.1093/aob/mcm307
Šmarda P, Hejcman M, Březinová A, Horová L, Steigerová H, Zedek F, Bureš P, Hejcmanová P, Schellberg J (2013) Effect of phosphorus availability on the selection of species with different ploidy levels and genome sizes in a long-term grassland fertilization experiment. New Phytol 200(3): 911–921. doi: 10.1111/nph.12399
Šmarda P, Knápek O, Březinová A, Horová L, Grulich V, Danihelka J, Veselý P, Šmerda J, Rotreklová O, Bureš P (2019) Genome sizes and genomic guanine + cytosine (GC) contents of the Czech vascular flora with new estimates for 1700 species. Preslia 91(2): 117–142. doi: 10.23855/preslia.2019.117
Soltis, DE, Soltis, PS, Bennett, MD, Leitch, IJ (2003) Evolution of genome size in the angiosperms. Amer J Bot 90(11): 1596–1603. doi: 10.3732/ajb.90.11.1596
Soltis DE, Soltis P, Tate JA (2004) Advances in the study of polyploidy since plant speciation. New Phytol 161(1): 173–191. doi: 10.1046/j.1469-8137.2003.00948.x
Soreng RJ, Davidse G, Peterson PM, Zuloaga FO, Judziewicz EJ, Filgueiras TS, Morrone O (2000 onwards) Catalogue of New World grasses (Poaceae). Available at: http://legacy.tropicos.org/Project/CNWG. Accessed 15 January 2024.
Soreng RJ, Bull RD, Gillespie LJ (2010) Phylogeny and reticulation in Poa L. based on plastid trnTLF and nrITS sequences with attention to diploids. In: Seberg O, Petersen G, Barfod AS, Davis JI (eds) Diversity, phylogeny, and evolution in the monocotyledons, Aarhus University Press, Aarhus, pp 619–643
Soreng RJ, Peterson PM, Romaschenko K, Davidse G, Teisher JK, Clark LG, Barberá P, Gillespie LJ, Zuloaga FO (2017) A worldwide phylogenetic classification of the Poaceae (Gramineae) II: an update and a comparison of two 2015 classifications. J Syst Evol 55(4): 259–290. doi: 10.1111/jse.12262
Soreng RJ, Peterson PM, Zuloaga FO, Romaschenko K, Clark LG, Teisher JK, Gillespie LJ, Barberá P, Welker CAD, Kellogg EA, Li D-Z, Davidse G (2022a) A worldwide phylogenetic classification of the Poaceae (Gramineae) III: an update. J Syst Evol 60(3): 476–521. doi: 10.1111/jse.12847
Soreng RJ, Gillespie LJ, Boudko EA, Cabi E (2022b) Biogeography, timing, and life-history traits in the PPAM clade: Coleanthinae (syn. Puccinelliinae), Poinae, Alopecurinae superclade, Miliinae, and Avenulinae and Phleinae (Poaceae, Pooideae, Poeae). J Syst Evol 60(3): 591–620. doi: 10.1111/jse.12811
Souza G, Costa L, Guignard MS, Van-Lume B, Pellicer J, Gagnon E, Leitch IJ, Lewis GP (2019) Do tropical plants have smaller genomes? Correlation between genome size and climatic variables in the Caesalpinia group (Caesalpinioideae, Leguminosae). Perspect Pl Ecol Evol Syst 38: 13–23. doi: 10.1016/j.ppees.2019.03.002
Stace CA (2005) Plant taxonomy and biosystematics – does DNA provide all the answers? Taxon 54(4): 999–1007. doi: 10.2307/25065484
Stace C (2022) Conspectus of and key to the world’s species of Vulpia C.C. Gmel. (Poaceae: Loliinae) and seven related genera. Brit Irish Bot 4(2): 74–94. doi: 10.33928/bib.2022.04.074
Stebbins GL (1950) Variation and evolution in plants, Columbia University Press, New York. doi: 10.7312/steb94536
Suda J, Krahulcová A, Trávníček P, Rosenbaumová R, Peckert T, Krahulec F (2007) Genome size variation and species relationships in Hieracium sub-genus Pilosella (Asteraceae) as inferred by flow cytometry. Ann Bot (Oxford) 100(6): 1323–1335. doi: 10.1093/aob/mcm218
Sumner AT (1990) Chromosome banding. Unwin-Hyman, London
Tadesse W, Sanchez-Garcia M, Gizaw Assefa S, Amri A, Bishaw Z, Ogbonnaya FC, Baum M (2019) Genetic gains in wheat breeding and its role in feeding the world. Crop Breed Genet Genomics 1: e190005. doi: 10.20900/cbgg20190005
Théroux-Rancourt G, Roddy AB, Earles JM, Gilbert ME, Zwieniecki MA, Boyce CK, Tholen D, McElrone AJ, Simonin KA, Brodersen CR (2021) Maximum CO₂ diffusion inside leaves is limited by the scaling of cell size and genome size. Proc R Soc B 288(1945): 20203145. doi: 10.1098/rspb.2020.3145
Theuri J, Phelps-Durr T, Mathews S, Birchler J (2005) A comparative study of retrotransposons in the centromeric regions of A and B chromosomes of maize. Cytogenet Genome Res 110(1–4): 203–208. doi: 10.1159/000084953
Tkach N, Ree RH, Kuss P, Röser M, Hoffmann MH (2014) High mountain origin, phylogenetics, evolution, and niche conservatism of arctic lineages in the hemiparasitic genus Pedicularis (Orobanchaceae). Molec Phylogen Evol 76: 75–92. doi: 10.1016/j.ympev.2014.03.004
Tkach N, Röser M, Suchan T, Cieślak E, Schönswetter P, Ronikier M (2019) Contrasting evolutionary origins of two mountain endemics: Saxifraga wahlenbergii (Western Carpathians) and S. styriaca (Eastern Alps). B M C Evol Biol 19: 18. doi: 10.1186/s12862-019-1355-x
Tkach N, Schneider J, Döring E, Wölk A, Hochbach A, Nissen J, Winterfeld G, Meyer S, Gabriel J, Hoffmann MH, Röser M (2020) Phylogeny, morphology and the role of hybridization as driving force of evolution in grass tribes Aveneae and Poeae (Poaceae). Taxon 69(2): 234–277. doi: 10.1002/tax.12204
Tkach N, Winterfeld G, Röser M (2024) Genome sizes of grasses (Poaceae), chromosomal evolution, paleogenomics and the ancestral grass karyotype (AGK). Preprint doi: 10.21203/rs.3.rs-3914153/v1
Tkach NV, Hoffmann MH, Röser M, von Hagen KB (2008) Temporal patterns of evolution in the Arctic explored in Artemisia L. (Asteraceae) lineages of different age. Plant Ecol Divers 1(2): 161–169. doi: 10.1080/17550870802331912
Trávníček P, Čertner M, Ponert J, Chumová Z, Jersáková J, Suda J (2019) Diversity in genome size and GC content shows adaptive potential in orchids and is closely linked to partial endoreplication, plant life-history traits and climatic conditions. New Phytol 224: 1642–1656. doi: 10.1111/nph.15996
Tutin TG (1952) Origin of Poa annua L. Nature 169: 160. doi: 10.1038/169160a0
Tutin TG (1957) A contribution to the experimental taxonomy of Poa annua L. Watsonia 4(1): 1–10. http://archive.bsbi.org.uk/Wats4p1.pdf
Tzvelev NN (1976) Zlaki SSSR [Grasses of the Soviet Union], Nauka, Leningrad.
Tzvelev NN, Probatova NS (2019) Zlaki Rossii [Grasses of Russia], KMK Scientific Press, Moscow.
Vaio M, Gardner A, Emshwiller E, Guerra M (2013) Molecular phylogeny and chromosome evolution among the creeping herbaceous Oxalis species of sections Corniculatae and Ripariae (Oxalidaceae). Molec Phylogen Evol 68(2): 199–211. doi: 10.1016/j.ympev.2013.03.019
Vaio M, Mazzella C, Porro V, Speranza P, López-Carro B, Estramil E, Folle GA (2007) Nuclear DNA content in allopolyploid species and synthetic hybrids in the grass genus Paspalum. Plant Syst Evol 265: 109–121. doi: 10.1007/s00606-006-0506-x
Valdés-Florido A, González-Toral C, Maguilla E, Cires E, Díaz-Lifante Z, Andrés-Camacho C, Nieto Feliner G, Arroyo J, Escudero M (2024) Polyploidy and hybridization in the Mediterranean: unravelling the evolutionary history of Centaurium (Gentianaceae), Ann Bot (Oxford) 134(2): 247–262. doi: 10.1093/aob/mcae066
Vallès J, Bašić N, Bogunić F, Bourge M, Brown SC, Garnatje T, Hajrudinović A, Muratović E, Pustahija F, Šolić EM, Siljak-Yakovlev S (2014) Contribution to plant genome size knowledge: first assessments in five genera and 30 species of angiosperms from western Balkans. Bot Serb 38(1): 25–33
Van de Peer Y, Ashman T-L, Soltis PS, Soltis DE (2021) Polyploidy: an evolutionary and ecological force in stressful times. Plant Cell 33(1): 11–26. doi: 10.1093/plcell/koaa015
Vogel KP, Arumuganathan K, Jensen KB (1999) Nuclear DNA content of perennial grasses of the Triticeae. Crop Sci (Madison) 39(3): 661–667. doi: 10.2135/cropsci1999.0011183X003900020009x
Walkowiak S, Gao L, Monat C, Haberer G, Kassa MT, Brinton J, Ramirez-Gonzalez RH, Kolodziej MC, Delorean E, Thambugala D, Klymiuk V, Byrns B, Gundlach H, Bandi V, Siri JN, Nilsen K, Aquino C, Himmelbach A, Copetti D, Ban T, Venturini L, Bevan M, Clavijo B, Koo DH, Ens J, Wiebe K, N’Diaye A, Fritz AK, Gutwin C, Fiebig A, Fosker C, Fu BX, Accinelli GG, Gardner KA, Fradgley N, Gutierrez-Gonzalez J, Halstead-Nussloch G, Hatakeyama M, Koh CS, Deek J, Costamagna AC, Fobert P, Heavens D, Kanamori H, Kawaura K, Kobayashi F, Krasileva K, Kuo T, McKenzie N, Murata K, Nabeka Y, Paape T, Padmarasu S, Percival-Alwyn L, Kagale S, Scholz U, Sese J, Juliana P, Singh R, Shimizu-Inatsugi R, Swarbreck D, Cockram J, Budak H, Tameshige T, Tanaka T, Tsuji H, Wright J, Wu J, Steuernagel B, Small I, Cloutier S, Keeble-Gagnère G, Muehlbauer G, Tibbets J, Nasuda S, Melonek J, Hucl PJ, Sharpe AG, Clark M, Legg E, Bharti A, Langridge P, Hall A, Uauy C, Mascher M, Krattinger SG, Handa H, Shimizu KK, Distelfeld A, Chalmers K, Keller B, Mayer KFX, Poland J, Stein N, McCartney CA, Spannagl M, Wicker T, Pozniak CJ (2020) Multiple wheat genomes reveal global variation in modern breeding. Nature 588: 277–283. doi: 10.1038/s41586-020-2961-x
Wang D, Zheng Z, Li Y, Hu H, Wang Z, Du X, Zhang S, Zhu M, Dong L, Ren G, Yang Y (2021) Which factors contribute most to genome size variation within angiosperms? Ecol & Evol 11(6): 2660–2668. doi: 10.1002/ece3.7222
Wang X, Morton JA, Pellicer J, Leitch IJ, Leitch AR (2021) Genome downsizing after polyploidy: mechanisms, rates and selection pressures. Plant J 107(4): 1003–1015. doi: 10.1111/tpj.15363
Wendel JF (2015) The wondrous cycles of polyploidy in plants. Amer J Bot 102(11): 1753–1756. doi: 10.3732/ajb.1500320
Wendel JF, Lisch D, Hu G, Mason AS (2018) The long and short of doubling down: polyploidy, epigenetics, and the temporal dynamics of genome fractionation. Curr Opin Gen Developm 49: 1–7. doi: 10.1016/j.gde.2018.01.004
Wentworth JE, Sieber VK, Ferris C (2004) An assessment of the origin of Alopecurus geniculatus L. based on 2C DNA amounts, NOR sites, RAPDs and cpDNA analysis. Watsonia 25(1): 137–155
Wieners RR, Fei S-Z, Johnson RC (2006) Characterization of a USDA Kentucky bluegrass (Poa pratensis L.) core collection for reproductive mode and DNA content by flow cytometry. Genet Resources Crop Evol 53(8): 1531–1541. doi: 10.1007/s10722-005-7766-0
Winterfeld G (2006) Molekular-cytogenetische Untersuchungen an Hafergräsern (Aveneae) und anderen Poaceae. Stapfia 86: 1–170. https://www.zobodat.at/pdf/STAPFIA_0086_0001-0170.pdf
Winterfeld G, Röser M (2007a) Disposition of ribosomal DNAs in the chromosomes of perennial oats (Poaceae: Aveneae). Bot J Linn Soc 155(2): 193–210. doi: 10.1111/j.1095-8339.2007.00690.x
Winterfeld G, Röser M (2007b) Chromosomal localization and evolution of satellite DNAs and heterochromatin in grasses (Poaceae), especially tribe Aveneae. Pl Syst Evol 264: 75–100. doi: 10.1007/s00606-006-0482-26
Winterfeld G, Döring E, Röser M (2009a) Chromosome evolution in wild oat grasses (Aveneae) revealed by molecular phylogeny. Genome 52(4): 1–20. doi: doi.org/10.1139/g09-012
Winterfeld G, Schneider J, Röser M (2009b) Allopolyploid origin of Mediterranean species in Helictotrichon (Poaceae) and its consequences for karyotype repatterning and homogenisation of rDNA repeat units. Syst Biodivers 7(3): 277–295. doi: 10.1017/S1477200009003041
Winterfeld G, Schneider J, Perner K, Röser M (2012) Origin of highly polyploids: different pathways of auto- and allopolyploidy in 12–18x species of Avenula (Poaceae). Int J Pl Sci 173(4): 1–14. doi: 10.1086/664710
Winterfeld G, Wölk A, Röser M (2016) Genome evolution in alpine oat-like grasses through homoploid hybridization and polyploidy. AoB PLANTS 8: plw039. doi: 10.1093/aobpla/plw039
Winterfeld G, Becher H, Voshell S, Hilu K, Röser M (2018) Karyotype evolution in Phalaris (Poaceae): the role of reductional dysploidy, polyploidy and chromosome alteration in a widespread and diverse genus. PLoS ONE 13(2): e0192869. doi: 10.1371/journal.pone.0192869
Winterfeld G, Ley A, Hoffmann MH, Paule, J, Röser M (2020a) Dysploidy and polyploidy trigger strong variation of chromosome numbers in the prayer-plant family (Marantaceae). Plant Syst Evol 306: 36. doi: 10.1007/s00606-020-01663-x
Winterfeld G, Paule J, Hoffmann MH, Ley A, Röser M (2020b) Antagonistic effects of whole-genome duplications and dysploidy on genome sizes in the pantropical monocot family Marantaceae: consequences in the light of a new molecular phylogeny. Curr Pl Biol 24: 100181. doi: 10.1016/j.cpb.2020.100181
Winterfeld G, Tkach N, Röser M (2023) Genome size variation and whole-genome duplications in the monocot order Poales. Preprint doi: 10.21203/rs.3.rs-3721310/v1
Winterfeld G, Tkach N, Röser M (2024) Reductional dysploidy and genome size diversity in Pooideae, the largest subfamily of grasses (Poaceae). Preprint doi: 10.21203/rs.3.rs-4359976/v1
Wölk A, Winterfeld G, Röser M (2015) Genome evolution in a Mediterranean species complex: phylogeny and cytogenetics of Helictotrichon (Poaceae) allopolyploids based on nuclear DNA sequences (rDNA, topoisomerase gene) and FISH. Syst Biodivers 13(4): 326–345. doi: 10.1080/14772000.2015.1023867
Xavier A, YadavR, Gowda V (2024) Evolutionary patterns of chromosome counts and genome size variations show positive correlations with taxonomic diversity in tropical gingers. Amer J Bot 111: e16334. doi: 10.1002/ajb2.16334
Yan H, Martin SL, Bekele WA, Latta R, Diederichsen AA, Peng Y, Tinker NA (2016) Genome size variation in the genus Avena. Genome 59(3): 209–220. doi: 10.1139/gen-2015-0132
Yang A, Chen X, Chen S (2023) Plant polyploidy: origin, induction, phenotypic change mechanisms, population establishment, and distribution. Preprint doi: 10.21203/rs.3.rs-2664888/v1
Yang L, Koo D-H, Li D, Zhang T, Jiang J, Luan F, Renner SS, Hénaff E, Sanseverino W, Garcia-Mas J, Casacuberta J, Senalik DA, Simon PW, Chen J, Weng Y (2014) Next-generation sequencing, FISH mapping and synteny-based modeling reveal mechanisms of decreasing dysploidy in Cucumis. Plant J 77(1): 16–30. doi: 10.1111/tpj.12355
Záveská E, Šída O, Leong-Škorničková J, Chumová Z, Trávníček P, Newman MF, Poulsen AD, Böhmová A, Chudáčková H, Fér T (2024) Testing the large genome constraint hypothesis in tropical rhizomatous herbs: life strategies, plant traits and habitat preferences in gingers. Plant J 117(4): 1223–1238. doi: 10.1111/tpj.16559
Zenil-Ferguson R, Ponciano JM, Burleigh JG (2016) Evaluating the role of genome downsizing and size thresholds from genome size distributions in angiosperms. Amer J Bot 103: 1175–1186. doi: 10.3732/ajb.1500408
Zhang L, Zhu X, Zhao Y, Guo J, Zhang T, Huang W, Huang J, Hu Y, Huang C-H, Ma H (2022) Phylotranscriptomics resolves the phylogeny of Pooideae and uncovers factors for their adaptive evolution. Molec Biol Evol 39(2): msac026. doi: 10.1093/molbev/msac026
Zhang M, Qiu X (2023) Genetic basis of genome size variation of wheat. Funct Integr Genomics 23: 285. doi: 10.1007/s10142-023-01194-x
Zhan SH, Otto SP, Barker MS (2021) Broad variation in rates of polyploidy and dysploidy across flowering plants is correlated with lineage diversification. Preprint doi: 10.1101/2021.03.30.436382
Zonneveld BJM, Leitch IJ, Bennett MD (2005) First nuclear DNA amounts in more than 300 angiosperms. Ann Bot (Oxford) 96(2): 229–244. doi: 10.1093/aob/mci170
Zonneveld BJM (2019) The DNA weights per nucleus (genome size) of more than 2350 species of the flora of The Netherlands, of which 1370 are new to science, including the pattern of their DNA peaks. Forum Geobot 8: 24–78. doi: 10.3264/FG.2019.1022

Tables 1 to 4 are available in the Supplementary Files section

No competing interests reported.

OnlineResource1.xlsx
Online Resource 1.xlsx
OnlineResource2Tables513.pdf
Online Resource 2.pdf
Table1.docx
Table2.docx
Table3.docx
Table4.docx

Download PDF

Reviewers invited by journal
05 Oct, 2024
Editor assigned by journal
04 Sep, 2024
Submission checks completed at journal
02 Sep, 2024
First submitted to journal
30 Aug, 2024

You are reading this latest preprint version

Genome size variation in the Poaceae supertribe Poodae, the major grass lineage of temperate climates (tribes Aveneae, Festuceae and Poeae)

Status:

Version 1

Abstract

Figures

Introduction

Material and Methods

Plant material

Measurement of genome sizes

Chromosome numbers, monoploid genome and mean chromosome sizes sizes (1Cx values and MCs)

Results and Discussion

Genome and chromosome size variation in the study group Poodae

Tribe Aveneae and its subtribes

Tribe Festuceae and its subtribes

Tribe Poeae and its subtribes

Intertribe hybrid groups

Are there any trends in the evolution of Poodae genome sizes?

Polyploidy (whole-genome duplication, WGD) and genome size

Dysploidy and change in genome and chromosome size

Different life forms and genome size

Conclusions

Declarations

Author Contribution

Acknowledgement

References

Tables

Additional Declarations

Supplementary Files

Status:

Version 1