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UBC Theses and Dissertations

The evolutionary origin of "black" kokanee (Oncorhynchus nerka) and their genetic and phenotypic diversity in the Anderson and Seton lakes system Moreira, Amanda Leigh


In order to conserve intraspecific biodiversity, it is crucial to identify genetic and phenotypic variation among populations and to understand the evolutionary processes that drive the evolution and persistence of such variation. Oncorhynchus nerka exists as two basic life history forms: the anadromous form, sockeye salmon and the non-anadromous form, kokanee. Unique populations of “black” kokanee are found in Lake Saiko, Japan, and in Anderson Lake and Seton Lake in the southwestern interior of British Columbia. They are distinct from other populations of O. nerka in that “black” kokanee spawn between 20 to 70 meters below the surface of each lake and spawn in the winter or early spring, whereas O. nerka typically spawns in the autumn in streams or shallow lake beaches. Using mitochondrial DNA and nine microsatellite loci, I investigated the evolutionary origin of eastern and western North Pacific populations of “black” kokanee. Both data sets support the hypothesis that “black” kokanee in Anderson Lake, Seton Lake and Lake Saiko have a polyphyletic origin resulting from repeated episodes of parallel evolution. Further, using variation at nine microsatellite loci, I demonstrated that “black” kokanee in the Anderson and Seton lakes system are genetically distinct from sympatric populations of sockeye salmon in Gates and Portage creeks, and that Anderson and Seton lake “black” kokanee are modestly distinct from one another. Anderson and Seton lake “black” kokanee differ dramatically from one another in standard length at maturity, but no differences were found between the two populations in size-adjusted maximum body depth or in gill raker numbers. My results provide an example of parallel evolution in north temperate freshwater fishes as well as evidence of yet another facet of distinctive biodiversity within O. nerka that needs to be recognized and accounted for in conservation planning for the taxon.

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