DISSERTATION RESEARCH: Species Boundaries and Phylogenetic Relationships in Chromosome Races of the Sceloporus grammicus Complex (Squamata).

Brigham Young University, Provo UT

Investigators

Abstract

A grant has been awarded from the National Science Foundation to Dr. Jack Sites and Mr. Jonathon Marshall, Brigham Young University, to study "Species boundaries and phylogenetic relationships of chromosome races of lizards of the Sceloporus grammicus complex in central Mexico." These lizards represent one of the most chromosomally variable of all non-mammalian vertebrate groups, and they have been described as textbook examples of how chromosomal mutations may facilitate the speciation process. Dr. Sites has spent over two decades of his research career studying speciation mechanisms in this group, and has accumulated a sufficiently large data base to make these lizards a "model system" for selected kinds of research. The objective of this study will be to test species boundaries across the eight chromosome 'races' known from central Mexico, using a minimum of four different methodologies. This will be accomplished by analyzing three different kinds of genetic markers, chromosomes, enzyme products analyzed by gel electrophoresis, and DNA sequences from three gene regions. Concordance among methods and data sets will be used to infer species boundaries, which should allow determination of causes for any possible conflicts among methods. This study has broad implications in the following context. Two frequently stated objectives of systematic biology are to: (1) discover the major 'natural groups' (= clades) of living species and how these are related, and (2) to discover species. The literature in systematic biology is very large with respect to theory and methods of tree-reconstruction to accomplish objective 1, but it is surprising limited with respect to objective 2, although the issue of delimitation of species is now getting increased attention. To date only a single study has been published comparing the performance of several methods (three), but the data set was limited, and Sites and Marshall can capitalize on the large data base for the S. grammicus complex to go far beyond anything previously attempted, and to contribute to the larger debate on delimiting species.