Fine‐scale bee species distribution models: Hotspots of richness and endemism in South Africa with species‐area comparisons

Abstract

While global patterns of bee diversity have been modelled, our understanding of fine‐scale regional patterns is more limited, particularly for under‐sampled regions such as Africa. South Africa is among the exceptions on the African continent; its bee fauna (ca. 1253 species) has been well collected and documented, including mass digitising of its natural history collections. It is a region with high floral diversity, high habitat heterogeneity and variable rainfall seasonality. Here, we combine a South African bee species distributional database (877 bee species) with a geospatial modelling approach to determine fine‐scale (~11 × 11 km grid cell resolution) hotspots of bee species richness, endemism and range‐restricted species. Our analyses, based on the probabilities of occurrence surfaces for each species across 108,803 two‐minute grid cells, reveal three bee hotspots of richness: Winter rainfall, Aseasonal rainfall and Early‐to‐late summer rainfall. These hotspots contain large numbers of endemic and geographically restricted taxa. Hotspots with particularly high bee diversity include the Fynbos, Succulent Karoo and Desert biomes; the latter showing 6–20 times more species per unit area than other biomes. Our results conform with global species‐area patterns: areas of higher‐than‐expected bee density are largely concentrated in Mediterranean and arid habitats. This study further enhances our knowledge in identifying regional and global hotspots of richness and endemism for a keystone group of insects and enabling these to be accounted for when setting conservation priorities.