Evolution of Species Richness

I developed phylogenetic methods to explore the taxonomic and geographic distribution of species richness within the flowering plants (angiosperms). I used both molecular and supertree techniques to reconstruct the evolutionary relationships among higher angiosperm taxa, and mapped the location of significant shifts in diversification rates on the angiosperm tree of life. I demonstrated that rate shifts have been much more frequent than previously assumed, and that simple explanations based upon one or a few key traits are insufficient to explain the highly labile nature of diversification rate (Davies et al. 2004a PNAS 101:1904-1909). I explored environmental influences on rates of diversification by extending the comparative method to include geographic information system (GIS) data within a phylogenetic framework. I used sister group comparisons to demonstrate that net speciation rates were greater in high-energy environments, and that environmental energy might also drive rates of molecular evolution, but independently (Davies et al. 2004b Proc. R. Soc. 271:2195-2200).

Supertree of the flowering plants – strength of shading reflects diversification rates – from low (light) to high (dark)