Hybridization Between Westslope Cutthroat Trout (Oncorhynchus Clarki Lewisi) and Rainbow Trout (O. Mykiss)
Author: Nathaniel P. Hitt
Publisher:
Published: 2002
Total Pages: 160
ISBN-13:
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Author: Nathaniel P. Hitt
Publisher:
Published: 2002
Total Pages: 160
ISBN-13:
DOWNLOAD EBOOKAuthor: Matthew Corsi
Publisher:
Published: 2011
Total Pages:
ISBN-13:
DOWNLOAD EBOOKThe role of introductions of nonnative fishes in the decline of native fishes cannot be overstated. Westslope cutthroat trout (Oncorhynchus clarkii lewisi, WCT) are a salmonid native to the northern Rocky Mountains. These trout hybridize with rainbow trout (O. mykiss, RBT) where they are sympatric; however, in portions of the WCT range where RBT have been introduced, hybridization appears to spread rapidly and threatens continued existence of WCT. The conservation value of these hybridized populations is equivocal, and a better knowledge of the ecological, demographic, behavioral, and genetic consequences of hybridization is needed to better inform conservation strategies. I investigated three related questions: specifically, what landscape factors are associated with estimates of introgression; what are life history differences between WCT and hybrids; and what are tradeoffs in restoring migratory life history in populations threatened by hybridization? The riverscape context plays a substantial role in the distribution of hybrids, as estimates of introgression declined with increases in stream slope, elevation, and distance from a primary source of RBT, three correlated landscape variables. Spatial variation in patterns of hybridization suggests clarifying objectives for sampling and careful designs are necessary to adequately understand the status of populations. Variation in location may relate to some of the ecological differences, such as growth, among fish with different levels of introgression. In the Jocko River, hybrids with ancestry> 20% RBT demonstrated higher growth, earlier migration, increased egg size, and lower fecundity versus WCT. These lines of evidence demonstrate the importance of limiting further hybridization even in populations that already have low levels of hybridization. Given that many unaltered populations currently reside in isolated habitat fragments, I evaluated several demographic tradeoffs of restoring a migratory life history weighed against the risks of increased potential for hybridization from removing barriers or selectively passing migratory fish above the barriers using both matrix and genetic population models. Restoration of migratory life history substantially increases population viability; however, hybridization in above-barrier population increases predictably relative to hybridization status of below-barrier population, which may reduce viability if vital rates are reduced in hybrids. Hybridization creates a challenging set of management problems, but this research adds several important pieces to the puzzles to help develop and evaluate conservation strategies.
Author: Michael D. Robinson
Publisher:
Published: 2007
Total Pages: 152
ISBN-13:
DOWNLOAD EBOOKAuthor: Clint Cain Muhlfeld
Publisher:
Published: 2008
Total Pages: 264
ISBN-13:
DOWNLOAD EBOOKAnthropogenic hybridization is one of the greatest threats to global biodiversity. Hybridization and introgression may lead to a loss of locally adapted gene complexes and ecological adaptations in native populations, yet these potential consequences have not been fully evaluated in nature. I investigated factors influencing the spread of hybridization between native westslope cutthroat trout (Oncorhynchus clarkii lewisi) and nonnative rainbow trout (O. mykiss) in the upper Flathead River system, Montana (USA) and British Columbia (Canada). The fundamental questions of my dissertation were: what are the behavioral, ecological, and fitness consequences of hybridization and what factors influence successful invasion of hybrids? First, I assessed the patterns of spawning between parental species and their hybrids and found that hybridization alters the spawning behavior of migratory westslope cutthroat trout, and is spreading via long distance dispersal of hybrids from downstream sources and some temporal overlap during spawning. Second, I describe for the first time how a wide range of levels of nonnative admixture affect fitness of cutthroat trout in the wild by estimating reproductive success in a recently invaded stream using parentage analysis with multilocus microsatellite markers. Small amounts of hybridization markedly reduced reproductive success, with fitness exponentially declining by ~50% with 20% nonnative genetic admixture. Finally, I evaluated the association of local-habitat features, landscape characteristics, and biotic factors with the spread of hybridization in the system, and found that hybridization increases in streams with warmer water temperatures, high land use disturbance and close proximity to the source of hybridization; however, none of these factors appeared sufficient to prevent further spread. These combined results suggest that hybrids are not only genetically different than westslope cutthroat trout but also have reduced fitness and are ecologically different, and that hybridization is likely to continue to spread if hybrid populations with high amounts of rainbow trout admixture are not reduced or eliminated. I conclude that extant aboriginal cutthroat trout are at greater conservation risk due to hybridization than previously thought and policies that protect hybridized populations need reconsideration.
Author: Matthew C. Boyer
Publisher:
Published: 2008
Total Pages: 12
ISBN-13:
DOWNLOAD EBOOKWe analyzed 13 microsatellite loci to estimate gene flow among westslope cutthroat trout, Oncorhynchus clarkii lewisi, populations and determine the invasion pattern of hybrids between native O. c. lewisi and introduced rainbow trout, Oncorhynchus mykiss, in streams of the upper Flathead River system, Montana (USA) and British Columbia (Canada). Fourteen of 31 sites lacked evidence of O. mykiss introgression, and gene flow among these nonhybridized O. c. lewisi populations was low, as indicated by significant allele frequency divergence among populations (?ST = 0.076, ?ST = 0.094, P
Author: Michael Patrick Peterson
Publisher:
Published: 2004
Total Pages: 78
ISBN-13:
DOWNLOAD EBOOKAuthor: M. M. Yau
Publisher:
Published: 2014
Total Pages: 8
ISBN-13:
DOWNLOAD EBOOKHybridization between rainbow trout (Oncorhynchus mykiss (Walbaum, 1792)) and westslope cutthroat trout (Oncorhynchus clarkii lewisi (Girard, 1856)) occurs commonly when rainbow trout are introduced into the range of westslope cutthroat trout. Typically, hybridization is most common in warmer, lower elevation habitats, but much less common in colder, higher elevation habitats. We assessed the tolerance to cold water temperature (i.e., critical thermal minimum, CTMin) in juvenile rainbow trout and westslope cutthroat trout to test the hypothesis that westslope cutthroat trout better tolerate low water temperature, which may explain the lower prevalence of rainbow trout and interspecific hybrids in higher elevation, cold-water habitats (i.e., the ?elevation refuge hypothesis?). All fish had significantly lower CTMin values (i.e., were better able to tolerate low temperatures) when they were acclimated to 15 °C (mean CTMin = 1.37 °C) versus 18 °C (mean CTMin = 1.91 °C; p
Author: Amy Kurant Matthews
Publisher:
Published: 2001
Total Pages: 184
ISBN-13:
DOWNLOAD EBOOKAuthor: J. D. McPhail
Publisher: University of Alberta
Published: 2007-09-28
Total Pages: 697
ISBN-13: 0888644671
DOWNLOAD EBOOKThe threat of deteriorating habitats and a loss of biodiversity make this reference work on the freshwater fishes of British Columbia more necessary than ever before. Eighty-one comprehensive species accounts aid accurate identification and consist of an illustration, the scientific and common names of the fish, its distinguishing characteristics, taxonomic comments, geographic distribution, a life-history summary, a habitat-use summary, and conservation comments. The book is a critical resource for biologists, naturalists, management and conservation officers, anglers, and members of the public who are concerned about our natural heritage. Foreword by Joseph S. Nelson.
Author: Steven T. Kalinowski
Publisher:
Published: 2010
Total Pages: 5
ISBN-13:
DOWNLOAD EBOOKWe describe 12 diagnostic single nucleotide polymorphism (SNP) assays for use in species identification among rainbow and cutthroat trout: five of these loci have alleles unique to rainbow trout (Oncorhynchus mykiss), three unique to westslope cutthroat trout (O. clarkii lewisi) and four unique to Yellowstone cutthroat trout (O. clarkii bouvieri). These diagnostic assays were identified using a total of 489 individuals from 26 populations and five fish hatchery strains.