Pollination is an essential ecosystem service primarily carried out by insects such as bees, butterflies, moths, flies (Elizalde et al., 2020; Rader et al., 2016, Bronstein et al., 2006; Magwira, 2021), wind (Culley et al., 2002), birds and bats (Kunz et al., 2011 and Ollerton & Coulthard, 2009) and humans through artificial means (Broussard et al., 2023). Pollination is considered as an important input to crop production and ecosystem functioning as it improves crop quality and quantity and maintenance of biodiversity and ecosystem resilience respectively (Alemberhe & Gebremeskel, 2016). It is through pollination that pollen from the male part of a flower (the stamen) is transferred to the female part (the stigma) of the same species (Asiko, 2012), which results in the fertilization of the ovules and production of seeds (Bronstein et al., 2006). Pollination enables the transfer of genetic material between plants (Abrol, 2012). A pollinator’s successful transfer of pollen is referred to as pollination efficiency (Brunet and Holmquist, 2009 and Keys et al., 2008). Over 70% of global food crops depend on pollinators (Ricketts et al., 2008) and without them, crop yields would be significantly reduced, impacting food security and the global economy (Gallai et al., 2009 and Khanna et al., 2021).
Insects particularly bees, are the most efficient pollinators (Osterman et al., 2021; Breeze et al., 2011; Stein et al., 2017). Their remarkable ability to transfer pollen between flowers significantly enhance the yield and fruit set of numerous crops (Dymond et al., 2021; Rauf et al., 2021; Fijen et al., 2018). Their pollination performance is largely attributed to their adeptness in moving from one flower to another (Cheng et al., 2016), their wide range availability (Musharraf et al., 2021) across different geographical conditions, their foraging behaviour and floral constancy (Alemberhe and Gebremeskel, 2016). Furthermore, their propensity to visit a diverse array of plant species further underscores their importance as pollinators (Stanley et al., 2020).
Apis mellifera is a species of bees belonging to the family Apidae and Genus Apis (Hilleman, 2009). They live in colonies and are known as eusocial insects (Papa et al., 2022) with a division of labour among the colony members. The body structure of Apis mellifera is highly adapted for pollination. This adaptation includes specialised hairs that facilitate pollen (Cheng et al., 2016). Additionally, they possess long tongues, enabling them to reach the nectar located at the base of flowers with long corollas (Borrell, 2005). Furthermore, their excellent color vision makes them particularly attracted to flowers with bright colors (Reser et al., 2012). Apis mellifera is a pollinator of Capsicum annum as they enhance productivity in fruit set and quality (Dag and Kammer, 2001).
Hypotrigona gribodoi margaretti are small, about 2–3 mm in body length (Asiko, 2012), dark-colored, stingless bees found in tropical, subtropical regions of the world and savanna ecosystems (Malovechko et al., 1995). They are eusocial insects (Chakuya et al., 2022) belonging to the family Apidae and subfamily Meliponinae. They forage on nectar and pollen enhancing pollination of more than 60% of different commercial crops (Heard, 1999, Atmowidi et al., 2022; Ramalho, 2004). Stingless bees have specialized structures called corbicula on their legs (Asiko, 2012) which enable them to efficiently gather and carry pollen. Their small body size allows them to pollinate small and delicate flowers that larger insects could potentially damage, thus making them important pollinators of many plant species in their natural habitats (Kasiera et al., 2022; Wakhungu et al., 2022 and Ndungu et al., 2019) and valuable contributors to the ecosystem (Slaa et al,. 2006). Hypotrigona gribodoi are pollinators of Capsicum annum as they enhance productivity by increasing the quality of fruit and fruit set rate (Kiatoko et al., 2014).
Capsicum annuum belongs to the genus Capsicum and the family Solanaceae (Pandey et al., 2012). It is a widely cultivated vegetable crop in different tropical and subtropical parts of the world (Pandey et al., 2012). Their flowers do not have poricidal anthers thus they do not require buzz pollination (Slaa et al,. 2006). Capsicum annum flowers produce both nectar and pollen (Greco et al., 2011) as flower reward to pollinators (Simpson and Neff, 1981). While the plant is capable of self-pollination, insect pollination can significantly enhance its productivity (Cruz et al., 2005; Greco et al., 2011).
An increase in agricultural activity leads to an increased demand for pollination services while activities associated with agriculture lead to pollinator decline (Aizen et al., 2009) thus creating a gap between pollination service demand and pollinators available to provide the services. Given the global concern over declining pollinator populations (Villanueva-G et al., 2005; Steffan-Dewenter et al., 2005) due to anthropogenic activities, including deforestation, habitat fragmentation, the use of pesticides (Chacoff, 2006; Li, 2019) and land use intensification and the expanding human population (Picanço et al., 2017), there is a growing global concern regarding the continuity of essential pollination services by insects (Allen-Wardell et al., 1998). As results, understanding the varying capacities of different pollinators has become imperative to effectively prioritize their conservation efforts.
The ecological role of stingless bees as pollinators for various plants (Norowi and Fahimie, 2010.) highlights their potential as promising alternatives for commercial crop pollination, emphasizing their importance (Slaa, 2006). Considering the importance of pollination services provided by bees, which enhance both the quality and quantity of crops and have a direct positive impact on the global economy and dietary outcomes (Musharraf et al., 2021), as well as their contribution to maintain plant species diversity, ensuring ecosystem resilience (Senapathi et al., 2015) and as outlined in the objectives of the Tanzania National Beekeeping Policy Implementation Strategy of 2021–2030 (URT, 2021), it is crucial to adopt conservation strategies that go beyond solely focusing on Apis mellifera as the only potential pollinator species. However, there is limited understanding of the pollination capacities of different bee species. While stingless bees show promise as commercial pollinators, their capacities compared to Apis mellifera remain insufficiently understood. This study aims to assess the differential efficiency of Apis mellifera and Hypotrigona gribodoi in pollinating Capsicum annuum and their impact on fruit set and yield. Finding from this study will have significance in improving the conservation of pollinators, ecosystem productivity, and crop production.