Guiding Field Surveys of Brazilian Vulnerable Baetidae (Ephemeroptera) through Species Distribution Modeling

The Atlantic Forest ranks among the most endangered tropical forests worldwide, only 28% of the original vegetation cover remains. Recent modeling studies indicate a drastic reduction in suitable habitat for all Ephemeroptera across the Atlantic Forest biome in the near future. Preliminary analyses of extinction risk in the Brazil considered four species of Baetidae (Ephemeroptera) as facing a significant risk of extinction, three of them endemic, with restricted distribution, and from the Atlantic Forest biome. Given the ecological importance and the limited distributional knowledge of these taxa, this study aims to apply current environmental modelling approaches to identify potential occurrence sites for three species ( Adebrotus lugoi, Camelobaetidius juparana , and Camelobaetidius spinosus ) that are at risk of extinction, thereby guiding field search for new populations. The models indicated restricted and fragmented distributions for Adebrotus lugoi, Camelobaetidius juparana , and C. spinosus , consistent with the habitat loss in the Atlantic Forest. Adebrotus lugoi showed a strong dependence on thermal stability variables (bio8, bio9), typical of groundwater-influenced streams, which contributes to its restriction to high-elevation areas. Camelobaetidius juparana was primarily influenced by slope (50.4%), being associated with steep, oxygen-rich streams characterized by stable substrates; it also exhibited sensitivity to precipitation seasonality (bio16, bio19). Camelobaetidius spinosus responded mainly to temperature seasonality (bio7) and precipitation during cold periods (bio19), indicating adaptation to high-elevation environments with pronounced thermal variation and reproduction synchronized with the dry winter season. These results highlight fine-scale niche differentiation among the species, with high thermal and hydrological specialization. The strong dependence on climatic variables—rather than on land use (13.4% contribution for A. lugoi )—suggests that climate change represents the main threat to their persistence. Conservation strategies should prioritize the identification and protection of thermal and hydrological microrefugia, as well as microhabitat-scale restoration. In this perspective, based on models were proposed priority sampling sites for each species.