The Tabanidae family ranks among the most abundant Diptera families worldwide, including those in the Neotropics (Coscarón and Papavero 2009, Henriques et al. 2012). Several species within this family are of importance in human and veterinary health, attributable to the hematophagous behavior of females, potentially acting as disease vectors (Mullens 2019). However, males play a crucial role in tropical ecosystems through their contributions to pollination (Goldblatt and Manning 2000). Consequently, aspects of natural history and behavior within these ecosystems have been historically documented.
In Ecuador, several biogeographical divisions and classifications have been proposed (refer to (Sierra 1999; Ridgely and Greenfield 2001; Freile and Santander 2005). Among these, the phytogeographic zone referred to as the Equatorial Pacific Region (EPR) (Peralvo et al. 2007; Espinosa et al. 2012) aligns predominantly with the Tumbesian or Jama-Zapotillo endemic region in the southern part (Cracraft 1985; Loaiza 2013) and the Chocó region in the northern part. This geographical area, which is also shared with Peru, is categorized into three distinct subregions based on its floristic characteristics. First, there are the provinces adjacent to the Chocó, including Esmeraldas and Los Ríos. Second, it encompasses the Peruvian provinces of Piura, Cajamarca, Lambayeque, and La Libertad. Third, it comprises the Ecuadorian provinces of Manabí, Guayas, Sta. Elena, El Oro, Loja, and Tumbes in Perú (Linares-Palomino et al. 2010; Espinosa et al. 2012).
The Ecuadorian EPR is used as a reference because a substantial portion of this phytogeographic area can be profoundly impacted by hydrological resources, such as water availability, during its two distinct seasons (Espinosa et al. 2012). Moreover, it is firmly established that tabanids exhibit a degree of dependency on these resources owing to the behavior of their larvae, which can display hydrophilic, semi-hydrophilic, or edaphic traits (Chvala 1972; Baldacchino et al. 2014a). Furthermore, this approach facilitates exploration of more refined subdivisions, a characteristic that is less evident within the Tumbesian region.
Within the EPR, extensive seasonal dry ecosystems span western Ecuador (Peralvo et al. 2007; Espinosa et al. 2012). These ecosystems have garnered a reputation as among the most imperiled in South America (Dodson and Gentry 1991), primarily attributable to anthropogenic factors such as deforestation and alterations in land use. Consequently, an astonishing 83% of these ecosystems are designated as areas exhibiting exceptionally low connectivity, with 86% of their total area falling into the highly threatened classification. Official data sources reported a deforestation rate of 23,618 hectares per year in the western Ecuadorian territory between 2016 and 2018 (Cueva-Ortiz et al. 2019; Rivas et al. 2020; MAE 2023).
Seasonally dry forests in the Pacific-Equatorial exhibit reduced species diversity, but have a pronounced degree of endemism, notably among vertebrates and flora (Chvala 1972; Cracraft 1985; Cueva-Ortiz et al. 2019). It is estimated that one in every five species within these ecosystems is endemic (Escribano-Avila et al. 2017). Furthermore, distinct sections of this region are recognized as one of the 25 global biodiversity hotspots. This designation falls into the category of Chocó Darién/Western Ecuador (Brooks et al. 2002).
In this biogeographic zone, few studies have been conducted on the diversity, distribution, and endemism of various groups, especially arthropods, including horseflies (Buestán 1980; Lattke et al. 2016; Escribano-Avila et al. 2017; Padrón et al. 2023). This implies that our understanding of the biological diversity of one of the most medically and ecologically relevant groups of blood-feeding insects in one of the least studied and highly threatened biogeographic zones in Ecuador and South America is limited. Therefore, the objective of this study was to provide a baseline by conducting an inventory of horsefly richness, endemism, and seasonal fluctuation in this important biogeographic zone.