Historical influences of volcanism and glaciation in shaping mitochondrial DNA variation and distribution in Yellowstone cutthroat trout across its native range

Abstract

While Yellowstone cutthroat trout Oncorhynchus clarkii bouvieri are probably the best known and one of the most extensively researched of all the subspecies of cutthroat trout, relatively little is knownabout their genetic structure and evolutionary history. In this study, we assessed the genetic variability and population structure among 50 populations of Yellowstone cutthroat trout over a large portion of their range in Idaho, Montana, Utah, Wyoming, and Nevada using restriction fragment length polymorphism and sequencing analysis of the mitochondrial ND1 and ND2 gene regions. Among the more than 1,000 samples analyzed, a total of 17 haplotypes were observed. These data indicate significant geographic structuring of the genetic variation between drainages and varying levels of reproductive isolation among populations within drainages. Much of this genetic structuring is clearly the product of long-term historical processes (basaltic volcanism and glaciations) that have isolated populations for substantial periods of time and then, in many cases, allowed secondary contact and subsequent admixture of divergent populations. Comparisons of samples between major basins were consistent with the results of previous allozyme and mtDNA investigations indicating that cutthroat trout in the Bear River basin in Utah have a more recent common ancestor with Yellowstone cutthroat trout than with the populations of Bonneville cutthroat trout O. c. utah in the central and southern portions of their range in Utah. The results from this study should assist managers with future conservation and management planning efforts for both subspecies. © American Fisheries Society 2011.