Within the tropics, precipitation has been shown to be correlated with plant species richness, but its effect on evolutionary diversity has not been explored. Here we bring together a novel and comprehensive database on the generic composition of angiosperm tree communities across lowland tropical South America (> 2,000 inventories from wet to arid biomes), and combine this with a new, large-scale phylogenetic hypothesis.
Results/Conclusions
We find marked reductions in the evolutionary diversity of communities as mean annual precipitation declines. However, evolutionary diversity does not continually increase with rainfall. Rather, in contrast to patterns observed for species richness, there is a decline in evolutionary diversity at the highest rainfall levels. Overall, our results suggest that the greatest number of angiosperm lineages can survive in intermediate precipitation regimes. Meanwhile, these areas of intermediate precipitation have been neglected in the design of protected area networks. We highlight areas of high evolutionary diversity that fall outside of protected areas and merit increased conservation attention.