Ecological and Evolutionary Drivers of Geographic Variation in Species Diversity

TLDR

Recent advances in phylogenetic and biogeographic data have enabled investigation of large‑scale species‑diversity gradients, revealing that biotic interactions likely enhance tropical diversification while energy availability plays a limited role. Fossil and phylogenetic evidence shows that tropical regions are the source of most taxa, comprising a mix of ancient and recent lineages, and that long‑term climatic stability and large tropical area have promoted speciation and reduced extinction, making climate stability and time‑integrated area the primary drivers of global diversity patterns.

Abstract

Recent studies have generated an explosion of phylogenetic and biogeographic data and have provided new tools to investigate the processes driving large-scale gradients in species diversity. Fossils and phylogenetic studies of plants and animals demonstrate that tropical regions are the source for almost all groups of organisms, and these groups are composed of a mixture of ancient and recently derived lineages. These findings are consistent with the hypothesis that the large extent of tropical environments during the past 10–50 million years, together with greater climatic stability, has promoted speciation and reduced extinction rates. Energy availability appears to only indirectly contribute to global patterns of species diversity, especially considering how some marine diversity gradients can be completely decoupled from temperature and productivity gradients. Instead, climate stability and time–integrated area together determine the baselines of both terrestrial and marine global diversity patterns. Biotic interactions likely augment diversification and coexistence in the tropics.