Patterns of Landscape Distribution, and Morphological and Genetic Variability in Cutthroat Trout of the Snake River Headwaters, Wyoming

We used a landscape scale approach to facilitate the synthesis of geomorphic, ecological, and genetic information regarding the distribution and organization of Yellowstone cutthroat trout, Oncorhynchus clarkii bouvieri, and finespotted Snake River cutthroat trout, Oncorhynchus clarkii subspecies, in the Snake River headwaters of northwest Wyoming. Selection criteria allowed us to hierarchically analyze for morphological or geographic structuring from the basin scale, to the stream reach scale. Multivariate morphometric analyses of spotting patterns can discriminate between the large and finespotted morphotypes when assessing fish that represent the extremes, although enough overlap in spotting patterns exist within the respective morphotypes to confound clear cut distinction. We were unable to genetically differentiate between the morphotypes using an 1,150 bp region of the ND2 mitochondrial genome. Genetic differences among drainages were apparent, and two distinct clades were present in the mtDNA dataset. Morphological and genetic differences were observed in rainbow-cutthroat hybrids that distinguished them from cutthroat trout, and hybridization was limited. Further genetic work is recommended using the existing sample set with nuclear markers, combined with additional collections from the main stem of the Snake River