Genetic Status of Isolated Populations of Colorado River Cutthroat Trout (Oncorhynchus clarkii pleuriticus) in the North Fork Little Snake River Drainage, Wyoming

Accidental conservation isolation characterizes a situation when a barrier created for a non-conservation purpose happens to fragment a population that now holds conservation value. This study established baseline genetic structure for the isolated populations of Colorado River cutthroat trout in the North Fork Little Snake River drainage, Wyoming. In many cases of accidental isolation, the populations above the barriers have limited habitat and small population sizes that make them vulnerable to extinction and may hold evolutionary value to the species as a whole. All the isolated populations in the drainage currently have high genetic differentiation among tributaries, low genetic diversity within each tributary, a suggestion of isolation by distance, and effective population sizes that are below the recommendation for long- term persistence. This structure represents natural and anthropogenic influences, but the presence of the human-constructed barriers in the headwater tributaries puts the larger core conservation group at risk into the future. Although the genetic diversities within the populations are low, the high genetic differentiations among populations suggest that each population may have its own unique contribution to the evolutionary value to the drainage as a whole and each is important to conserve into the future.