Yellowstone National Park Report
Cutthroat, Salmo clarki, and rainbow, Salmo gairdneri, trout are largely allopatric, closely related species. Where naturally sympatric ecological isolating mechanisms maintain species identity. However, the inland subspecies of cutthroat trout which did not evolve in sympatry with rainbows are thought to freely hybridize with rainbow trout which have been introduced for recreational purposes. Because of the mass introductions of rainbow trout fish managers have become increasingly concerned about the purity of the dwindling stocks of native cutthroats.
Loudenslager, Eric J. and Gall, G. A.E.
"Hybridization between Cutthroat and Rainbow Trout: Evidence from Biochemical Genetic Loci,"
University of Wyoming National Park Service Research Center Annual Report: Vol. 3
, Article 21.
Available at: http://repository.uwyo.edu/uwnpsrc_reports/vol3/iss1/21