Evolutionary history and global angiosperm species richness–climate relationships

Aim: Climate has been regarded as an important explanation for large-scale species richness patterns. However, the mechanisms underlying the significant variations in species richness–climate relationships across different clades remain to be tested. We explored how niche conservatism, diversification rates and time for speciation influenced species richness–climate relationships between clades. Location: The globe. Time Period: Present day. Major Taxa Studied: Angiosperms. Methods: Based on a newly complied database of the global distributions of 288,735 angiosperm species, we used generalized linear models to assess the relationships between species richness of different angiosperm families and climatic factors. We also conducted phylogenetic comparative analysis to test whether niche conservatism, diversification rates and time for speciation affect the variations in species richness–climate relationships. Results: We found that temperature seasonality dominated the global angiosperm diversity patterns. Closely related families had more similar species richness–climate relationships than distantly related ones. The discrepancy between the current and ancestral niches of different clades had much stronger effects on variations in species richness–climate relationships than diversification rates and time for speciation. With the increase in the discrepancy between current and ancestral niches, the explanatory power (i.e., R²) of contemporary temperature and precipitation in explaining species richness patterns increased. Main Conclusions: Overall, our findings strongly support that niche conservatism dominates the variations in species richness–climate relationships across taxonomic groups. These findings allow better understanding on how large-scale species diversity patterns are formed.