Molecular Systematics of Rodents

University Of Cincinnati Main Campus, Cincinnati OH

Investigators

Abstract

0075306 deBry Living rodents comprise about one half of all extant mammals - a total of over 2,000 species classified into about 32 families. Resolving the evolutionary relationships among these families has resisted over 100 years of study, primarily using morphological characteristics. Previous studies of rodent phylogeny using DNA sequence data have resulted in only minimal resolution of deep relationships. This study will both increase the number of rodent and non-rodent species examined and substantially increase the amount of DNA sequence data per species, compared to those previous DNA sequence studies. Over 5,000 base pairs of DNA sequence data will be collected, from portions of five different nuclear protein-coding genes from 46 representative rodent species and 14 non-rodent outgroups. The study is designed to maximize cohesion with other, ongoing studies of mammalian phylogeny, of both deeper (inter-ordinal) and more recent (intra-familial) divergences. Data obtained will also be used to address several aspects of one of the most fundamental questions in molecular evolution: how and why nucleotide and protein sequences change over time. Three specific hypotheses will be tested: 1) changes in protein structure can convert nucleotide positions that were previously invariable into positions that can be varied; 2) the primary determinant of the rate of molecular evolution is generation time; 3) natural selection on translational accuracy is capable of causing non-random usage of synonymous codons. The tests of all three of these hypotheses are thoroughly integrated with the phylogenetic aspect of this project. Rodents, by virtue of their rich species diversity and access to many different nuclear gene sequences, are perhaps the best model system with which to address these important evolutionary process questions.