9615163 HONEYCUTT Rodents represent a major component of mammalian diversity worldwide. They demonstrate considerable variation in morphology, habitat utilization, behavior, life history strategies, and biogeographic distribution. At the DNA sequence level, rodents demonstrate faster overall rates of change than seen for other groups of mammals, and this increase in nucleotide substitution rate has been linked to differences in generation time and overall mutation rates. The purpose of this research, to be conducted by Rodney Honeycutt, is twofold. First, nucleotide sequence data from three nuclear genes and one mitochondrial gene will be used to investigate relationships among rodents in the suborder Histricognathi. This suborder encompasses a large subset of rodent diversity, including a majority of rodent families. Histricognath rodents occur primarily in Africa and South America, and within South America they represent an unique part of the mammalian radiation. Second, these nucleotide sequence data and the resulting gene trees will be used to examine patterns of change at the molecular level. Some of the patterns to be investigated pertain to correlation's between heterogeneity in the rate of nucleotide substitution and several parameters including body size, metabolic rate, and generation time. In an effort to determine whether or not rodent genes experience different classes of substitutions relative to other mammals, both the distribution of nucleotide substitutions throughout each gene and rates of change in all these genes will be compared to those seen in other non-rodent mammal groups.
