Desert Fishes Council, Death Valley, California, November 2009.

Cutt through the bull trout, a mitochondrial DNA phylogeny of Oncorhynchus clarkii, Cutthroat Trout.

P.J. Unmack & D.K. Shiozawa

Approximately 14 subspecies of Oncorhynchus clarkii, Cutthroat Trout are recognized from western North America. Most populations are seriously threatened or endangered mostly due to introgression, predation and competition from introduced trouts as well as general habitat degradation. Many of these impacts occurred so early that the original distributions of some subspecies are incompletely known. Much genetic work has been conducted on different subspecies mostly aimed at determining levels of introgression. Here we present data from four protein coding mitochondrial genes in a combined analysis to investigate broader phylogenetic patterns across the range of the species. Three main groupings were found, a basal cluster consisting of O. c. clarkii, Coastal Cutthroat Trout, O. c. henshawi, Lahontan Cutthroat Trout and O. c. lewisi, Westslope Cutthroat Trout. The last two groups are sister lineages, with one consisting of O. c. bouvieri, Yellowstone Cutthroat Trout and O. c. sp., Bear River Cutthroat Trout. The last lineage consists of O. c. pleuriticus, Colorado River Cutthroat Trout, O. c. stomias, Greenback Cutthroat Trout, O. c. virginalis, Rio Grande Cutthroat Trout and O. c. utah, Bonneville Cutthroat Trout. We found moderate to strong resolution between the three lineages, but mostly poor resolution within each lineage. Aspects of the biogeographic history of the group will be discussed and compared with previous hypotheses.