Genetic variation is widely recognized as a major component of species
biodiversity, contributing greatly to the maintenance of adaptive potential in
populations and their evolutionary response to change. Despite years of study and
their obvious importance to evolution and conservation biology, however, the
biological processes responsible for the maintenance of genetic variation in the wild
are still poorly understood. Throughout this thesis, I have attempted to describe the
historical and contemporary forces contributing to the origins and maintenance of
genetic variation in coastal cutthroat trout (Oncorhynchus clarkii clarki), a salmonid
characterized by small population sizes and one that is of growing conservation
concern in western North America. I found evidence for the existence of three, and
possibly four glacial refugia for coastal cutthroat trout and a complex pattern of
secondary contact between refugial groups in the northern portion of their range.
Over subregional scales, both long term and contemporary estimates of gene flow
between adjacent populations appear on the order of one migrant per generation,
the theoretically optimal level to reduce the loss of genetic diversity in small
populations. I also found evidence that interspecific gene flow between coastal
cutthroat and rainbow trout (O. mykiss) may be widespread in populations
throughout the study area. Finally, through an intensive demographic and genetic
study of a single representative population, I found that the breeding system of
coastal cutthroat trout may itself compensate for the small, fluctuating number of
spawners typical of the subspecies. Mating patterns were found to be quite complex
ranging from monogamy to polygynandry, with mating occurring between different
cohorts and life history types. My results go further, suggesting that genetic
compensation, in the form of an increase in levels of polyandry and a reduction in
the variance associated with female reproductive success, partially countered
fluctuations in population size. I discuss the key findings of each chapter as they
pertain to the maintenance of genetic variation in small populations, the future
conservation of coastal cutthroat trout, and, more generally, in terms of applied
salmonid management. / Science, Faculty of / Zoology, Department of / Graduate
| Identifer | oai:union.ndltd.org:UBC/oai:circle.library.ubc.ca:2429/30770 |
| Date | January 2006 |
| Creators | Costello, Allan |
| Publisher | University of British Columbia |
| Source Sets | University of British Columbia |
| Language | English |
| Detected Language | English |
| Type | Text, Thesis/Dissertation |
| Rights | For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use. |
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