Estimating global bee species richness and taxonomic gaps

Robust species richness estimates are critical for meaningful conservation prioritisation, understanding ecosystem resilience, and studying evolutionary processes. Yet, they remain elusive even for some of the best-studied groups and regions. As keystone pollinators, bees are crucial for the maintenance of healthy ecosystems, yet rigorous estimates of their species richness are lacking. Here, we statistically estimate global, continental, and country lower bounds of bee species richness. Globally, we estimate 24,705-26,164 bee species, an 18-25% increase, representing at least 32-45 years of taxonomic research. We estimate particularly high undescribed biodiversity from Asia, Africa, and the Americas. We find that taxonomic gaps are correlated with gross domestic product per capita (GDPc), observed species richness, number of occurrence records, and completeness of occurrence databases. Our statistical R-package framework will progress our understanding of lesser-known groups, downstream consensus, and mobilise existing occurrence datasets to quantitatively estimate species richness on global scales.