Spread of hybridization between native westslope cutthroat trout, Oncorhynchus clarki lewisi, and nonnative rainbow trout, Oncorhynchus mykiss

Canadian Journal of Fisheries and Aquatic Sciences
By: , and 

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Abstract

We examined spatial and temporal patterns of hybridization between native westslope cutthroat trout, Oncorhynchus clarki lewisi, and nonnative rainbow trout, O. mykiss, in streams of the Flathead River system in Montana, U.S.A. We detected hybridization in 24 of 42 sites sampled from 1998 to 2001. We found new Oncorhynchus mykiss introgression in seven of 11 sample populations that were determined to be nonhybridized in 1984. Patterns of spatial autocorrelation and linkage disequilibrium indicated that hybridization is spreading among sites and is advancing primarily via post-F1 hybrids. Although hybridized populations were distributed widely throughout the study area, the genetic contribution from O. mykiss decreased with increasing upstream distance from the Flathead River mainstem, suggesting that O. mykiss introgression is spreading in an upstream direction. The spread of hybridization may be constrained more by demographic than by environmental factors, given that (i) hybridized populations generally encompassed the range of environmental variability in nonhybridized populations, and (ii) hybridization status was more strongly associated with neighborhood statistics than measured environmental gradients.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Spread of hybridization between native westslope cutthroat trout, Oncorhynchus clarki lewisi, and nonnative rainbow trout, Oncorhynchus mykiss
Series title Canadian Journal of Fisheries and Aquatic Sciences
DOI 10.1139/f03-125
Volume 60
Issue 12
Year Published 2003
Language English
Publisher Canadian Science Publishing
Contributing office(s) Northern Rocky Mountain Science Center
Description 12 p.
First page 1440
Last page 1451
Country United States
State Montana
Other Geospatial Flathead River, Middle Fork River, North Fork River
Online Only (Y/N) N
Additional Online Files (Y/N) N