Geographically divergent evolutionary and ecological legacies shape mammal biodiversity in the global tropics and subtropics.

Studies of the factors governing global patterns of biodiversity are key to predicting community responses to ongoing and future abiotic and biotic changes. Although most research has focused on present-day climate, a growing body of evidence indicates that modern ecological communities may be significantly shaped by paleoclimatic change and past anthropogenic factors. However, the generality of this pattern is unknown, as global analyses are lacking. Here we quantify the phylogenetic and functional trait structure of 515 tropical and subtropical large mammal communities and predict their structure from past and present climatic and anthropogenic factors. We find that the effects of Quaternary paleoclimatic change are strongest in the Afrotropics, with communities in the Indomalayan realm showing mixed effects of modern climate and paleoclimate. Malagasy communities are poorly predicted by any single factor, likely due to the atypical history of the island compared with continental regions. Neotropical communities are mainly codetermined by modern climate and prehistoric and historical human impacts. Overall, our results indicate that the factors governing tropical and subtropical mammalian biodiversity are complex, with the importance of past and present factors varying based on the divergent histories of the world's biogeographic realms and their native biotas. Consideration of the evolutionary and ecological legacies of both the recent and ancient past are key to understanding the forces shaping global patterns of present-day biodiversity and its response to ongoing and future abiotic and biotic changes in the 21st century.