DNA Data Support a Rapid Radiation of Pocket Gopher Genera (Rodentia: Geomyidae)

In this study, we address the question of phylogenetic relationships in the Geomyidae, focusing primarily on intergeneric relationships within the tribe Geomyini. Our study makes use of DNA sequences from two mitochondrial and two nuclear genes, and we use model-based methods of phylogenetic analysis to infer relationships and determine the level of support for each proposed relationship. Relationships among geomyine pocket gopher genera remain only partially resolved despite a number of earlier attempts to reconstruct their phylogenetic history and despite the newly generated sequence data analyzed in this study. This lack of resolution does not appear to result from insufficient or inappropriate DNA data, nor is it caused by inadequate sampling of taxa. Rather, molecular data and fossil data together lead to the conclusion that diversification within the Geomyini likely occurred during a geologically brief period in the Blancan. Rapid climate change during the Blancan, the origin of patchily distributed grasslands, and the evolution of hypsodonty may have triggered the rapid diversification that eventually produced the five extant genera of the Geomyini.