New lab study online at Ecology Letters
Using a complete species level phylogeny and detailed information on species traits, we find that neither ecological constraints nor diversification rates contribute substantially to worldwide richness gradients of mammals and birds. In contrast, region size and history emerge as major determinants which act similarly in birds and mammals despite important differences in the relationship between traits structure and diversification. The results are surprising because they show that both diversification rates and ecological constraints are generally only weakly associated with broad-scale variation in species richness. Rather, regional history and, to a lesser degree, region environment are the more dominant predictors of large-scale diversity gradients.