Friday, April 26, 2013
R. Alexander Pyron, PhD
Robert F. Griggs Professor of Biology, The George Washington University
The extraordinary diversity of life is a striking feature of the natural world. The concentration of biodiversity in the tropics is one of the oldest-known patterns in ecology and evolution, yet no comprehensive explanations have been proposed to account for this on a global scale. Crucially, only three processes can affect the spatial distribution of species richness: speciation, extinction, and dispersal. These can be simultaneously evaluated only using information on the evolutionary relationships of species in the form of a phylogeny. I have generated a phylogeny using DNA sequence data for a large proportion of the globe's caecilians, salamanders, and frogs. Using mathematical models, I find that that high tropical diversity is explained by higher speciation in the tropics, higher extinction in temperate regions, and low dispersal out of the tropics, all associated with climate. Further evidence suggests that ecological factors limit accumulation of biodiversity at higher latitudes.
