My research is involved with understanding phylogenetic and biogeographic components of biological diversity, focusing on freshwater fishes, although I am interested in other aquatic organisms. Much of my work has direct bearing on the conservation of North American fishes and includes both museum-based, alpha-level taxonomy (e.g., description of a new species of sucker, Catostomus, from Nevada) and laboratory-based studies of population and conservation genetics (e.g., Cahaba shiner, Notropis cahabae, from the Mobile Basin of Alabama). In order to address various questions, I use a variety of tools, including traditional (e.g., morphological, ecological, life history, and behavioral characters) and molecular characters, historical and ecological biogeography, paleoecology, paleohydrology and population genetics. Integrating these conceptual areas falls within the context of the disciplines of phylogenetics, phylogeography, and conservation genetics. I am particularly interested in examining the extent to which currently widespread "taxonomic" species represent phylogenetically distinct evolutionary lineages with associated geographic structure. For example, I have been working on the molecular phylogenetic relationships among "subspecies" of tui chubs (Siphateles bicolor complex) in the Great Basin. Based on this work, what was once one widely-distributed, polytypic species is now recognized as nine species (several of which are threatened and endangered). In addition to taxonomy and systematics, this is one of the first studies to examine the biogeography of aquatic ecosystems in the Great Basin and relate patterns of genetic diversity with the paleohydrology of the Lahontan Basin and adjoining basins. Similar work on minnows of the genus Campostoma (stonerollers) from the eastern and southeastern United States and Mexico indicates that mtDNA haplotypes in the two most widespread species (C. anomalum and C. oligolepis) are structured geographically, rather than phylogenetically, indicating that both "species" are composites of multiple independent lineages. In addition, the geographic distribution of recovered clades coincides with known paleohydrological basins, particularly in the southeastern U.S. This geographic structuring has been consistently recovered in other research done in collaboration with Dr. Richard L. Mayden (Saint Louis University) on North American minnows (Notropis), suckers (Moxostoma and Scartomyzon) and sunfishes and basses, and has been reported in the literature for crayfishes and freshwater mussels. This work on phylogenetic relationships and biogeography has important implications for not only ichthyology but also conservation and management of aquatic fauna. First, it seems clear that the current taxonomy of many species will need revision. Having a phylogeny will provide the requisite historical framework in which to re-evaluate patterns of morphological, behavioral, and ecological variation and revise our understanding of the composition of, and limits to, these species. Secondly, better understanding of the composition of species and their distributions facilitates identification of areas of endemism and/or management units for conservation efforts.