Global bee bioregions mirror those of other taxa despite a uniquely bimodal latitudinal diversity gradient

Bioregionalization, the partitioning of the globe into areas of biotic similarity, is one of nature's most striking patterns, and highly congruent boundaries have been identified across plants, tetrapods, ants, and butterflies. However, these taxa also share a unimodal latitudinal diversity gradient (LDG), raising the question of whether bioregionalization and the LDG are mechanistically coupled or instead arise from largely independent processes acting on different timescales. Bees (Hymenoptera: Anthophila) provide a natural test, their diversity peaking at mid-latitudes rather than in the tropics. Using range estimates for 3,370 species and a phylogenetic beta-diversity framework, we recover 21 bee bioregions nested within at least six major realms (Australasia, Indomalaya-Oceania, Nearctic, Neotropics, Palearctic, and Sub-Sahara) that closely align with those of other taxa despite bees' atypical diversity gradient. We propose that bioregionalization and species richness are decoupled because they arise from distinct processes: the former reflects historical dispersal and evolutionary history, the latter local diversification, extinction, and environmental filtering. Our analysis provides a global biogeographic framework for future bee research and highlights the processes shaping the world's major biogeographic boundaries.