This thesis addresses the issue of hybridization between native westslope cutthroat trout
(Oncorhynchus clarkii lewisi) and introduced rainbow trout (O. mykiss), giving strong
consideration to their differing glacial refugia during the Wisconsin Glaciation. We
hypothesize that having more recently derived from an anadromous form O. mykiss will
possess life history characteristics more typical of a highly anadromous species. This
hypothesis would also predict hybrids to be intermediate in these characteristics. In a
comparison of growth rates and survivorship (Chapter 2) O. clarkii lewisi were found to
employ a slower growing, longer lived strategy than O. mykiss, with hybrids typically
being intermediate. Additionally, O. mykiss were also found to have aerobic and
anaerobic metabolic capacities superior to O. clarkii lewisi in a first time comparison of
these species (Chapter 3). These results support the glacial refuge hypothesis, but
furthermore provide a potential explanation of the establishment of the elevational
gradient commonly observed in hybridization studies. It would seem likely that O. mykiss
would require more productive reaches being a faster growing, shorter lived species with
higher metabolic costs. This study confirmed the gradient of O. mykiss persisting at lower
elevations, trending through a hybrid zone to pure O. clarkii lewisi in headwater reaches
and above migratory barriers (Chapter 2). A similar gradient was also reported when
considering only the hybrid population, supporting the notion that habitat preference is
under some genotypic control. The importance of migratory barriers was found to
decrease with elevation suggesting potential additional limiting factors. Hybrid
individuals were also found to be intermediate in morphological characteristics (Chapter
4). The confidence in differentiating between pure and non-pure O. clarkii lewisi was found to increase with the number of O. mykiss alleles (degree of hybridization) an
individual possessed. Morphological-based identification was found to be an efficient,
cost-friendly, preliminary assessment tool that could be useful in limiting the number of
sites needing detailed genetic assessment. / 152 leaves : ill. (some col.) ; 29 cm.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:ALU.w.uleth.ca/dspace#10133/672 |
| Date | January 2007 |
| Creators | Robinson, Michael D., University of Lethbridge. Faculty of Arts and Science |
| Contributors | Rasmussen, Joseph |
| Publisher | Lethbridge, Alta. : University of Lethbridge, Faculty of Arts and Science, 2007, Arts and Science, Department of Biological Studies |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | en_US |
| Detected Language | English |
| Type | Thesis |
| Relation | Thesis (University of Lethbridge. Faculty of Arts and Science) |
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