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Show Thomas E. Dowling ( presenter) W. L. Minckley Department of Biology Arizona State University Tempe, AZ 85287- 1501 Thomas. Dowling@ ASU. EDU Fish Genetics and Evolution BIOGEOGRAPHIC ANALYSIS OF GREAT BASIN FISHES: POTENTIAL AND PITFALLS In their original treatment of the zoogeography of the Great Basin, Hubbs and Miller inferred history of the region by correlating past and present distributions of fishes with hydrological and physiographic factors. They emphasized the complementary nature of information obtained from these sources and the need for additional studies to provide greater understanding of the history of this basin. Advances in molecular methodology have contributed additional characters for biogeographic studies, with mitochondrial DNA ( mtDNA) possessing several properties that make it particularly useful for this purpose. Variation in the nucleotide sequence of this molecule has provided resolution of phylogenetic relationships in many groups of fishes. These inferred evolutionary histories are often consistent with geological events, illustrating the value of this approach for biogeographic studies. Several groups of fishes from the Great Basin deserts and adjacent regions have been the subjects of molecular studies, providing information on phylogenetic and biogeographic relationships for several groups of fishes. While these studies identify the potential of molecular characters in expanding our understanding of the Great Basin, synthesis of information across the entire region has not been attempted. We present biogeographic information obtained from studies of mtDNA variation in minnows ( Cyprinidae). This diverse group of fishes is ideally suited for this purpose, represented by a series of endemic taxa and other forms found throughout the region. Analysis of mtDNA variation revealed a complex history for drainages of the Great Basin. Phylogenetic placement of the narrowly distributed monotypic genera Eremichthys and Relictus is not well- resolved relative to other western North America cyprinids, but their placement is consistent with early origins proposed by Hubbs and Miller. Phylogenetic analysis of broadly distributed taxonomic groups revealed a complex pattern of relationships, involving both recent and ancient connections of the Great Basin with the Snake and Colorado rivers. Phylogenetic analysis of the subfamily Plagopterini ( the genera Lepidomeda, Meda, Plagopterus, and Gila [ Snyderichthys] copei) supports a previously hypothesized connection between the Snake and Colorado rivers through the pluvial White River. Potential difficulties associated with introgressive hybridization are also evident, complicating attempts to infer phylogenetic relationships among these taxa. In spite of these obstacles, mtDNA has been useful for tracing the history of maternal lineages and historical connections among drainages. Shared mtDNA characters between Gila atraria from the Bonneville basin and Gila cypha from the Colorado basin indicated past connections between |