9213281 Cipriano A variety of related plant and animal taxa, both marine and terrestrial, are found to the north and south of an apparent tropical barrier. The variety of these "antitropical" taxa includes many supposed populations or species pairs of whales, dolphins and porpoises. This project will study the relationships and divergence between dolphin species of the genus Lagenorhynchus found in northern and southern temperate oceans and will test alternative hypotheses of Pleistocene glaciation or mid-Miocene warming as explanations for the currently observed anti-tropical species distributions. Sequence analysis of portions of dolphin mitochondrial DNA, with supplemental use of nuclear DNA markers, will be used to establish relationships within the genus, and for comparison to related outgroup genera also within the the Family Delphinidae. In order to place amounts of genetic divergence found between Lagenorhynchus species into perspective, it will be necessary to sequence specimens from populations within Lagenorhynchus species to provide a yardstick for interpreting interspecific divergence. This project will also investigate the population structure of white- sided dolphins (L. obliquidens) found continuously distributed in the North Pacific, and of widely separated populations of dusky dolphins (L. obscurus) from the southern oceans. This would be the first attempt to establish genetic criteria for distinction of stocks of these species, or to recognize potential specific status of L. obscurus from different areas. This information may be useful to determine whether particular stocks are at risk form fishing activities in certain regions. In order to assess the approximate timing of the divergence between Lagenorhynchus species, genetic distances will be interpreted using the perspective provided by population structure analysis, comparison to published sequences for outgroups, and comparison to genetic distances of other taxa known to have div erged in Miocene and Pleistocene times. Because of the large difference between the time scale of the two alternatives, identification of the congruence of Lagenorhynchus divergence timing with one should thus be possible even without a rate calibration. ***
