Historical diversification of montane herpetofauna within and between the sierras of Mexico

Historical Diversification of Montane Herpetofauna Within and Between the Sierras of Mexico by Robert W. Bryson, Jr. Dr. Brett R. Riddle, Examination Committee Chair Professor of Biological Sciences University of Nevada, Las Vegas The Mexican highlands consist of four major mountain ranges spanning most of mainland Mexico. The evolutionary history of the Mexican highlands has been shaped by various geological and climatic events over the past several million years. The relative impacts of these historical events on diversification in montane taxa, however, remains uncertain. I used mitochondrial DNA data from three widely distributed species complexes of lizards as a model system to exemplify the potential roles of Neogene mountain formation and Quaternary climate change on timing and tempo of diversification across the Mexican highlands. My results suggested strong geographic partitioning of genetic variation across Mexico in all three lizard groups. There appeared to be a generalizable anchor of diversification across taxa centered around the development of the Transvolcanic Belt. Diversification across the rest of the Mexican highlands was largely idiosyncratic, but filter barriers such as river drainages likely subdivided lineages differentially through time. Diversification patterns observed in my three focal groups of lizards provide additional insight into the mechanisms that impacted differentiation of highland taxa across the complex Mexican highlands.