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An examination of two reported protein polymorphisms in threespine stickleback, Gasterosteus aculeatus

University of British Columbia

Gasterosteus aculeatus L., the threespine stickleback is in morphological terms, an extremely variable species. It is found in a wide variety of habitats throughout the northern hemisphere. Forms of threespine stickleback are found in anadromous and freshwater situations. Taxonomic examinations concerning the distribution of various forms of stickleback have produced equivocal results. Two stickleback protein polymorphisms have been reported in the literature. A hemoglobin polymorphism has been found in south European stickleback, and a muscle myogen polymorphism (enzyme: creatine kinase) has been found in stickleback from western Canada. The distribution of alleles in both these situations caused the researchers to hypothesize that the polymorphisms were related to the anadromous existences of certain forms of stickleback. In this study I tested these hypotheses with populations from southwestern British Columbia, across a range of macro-habitat types. One population of sticklebacks sampled is, apparently, a relict anadromous population. This population provided the opportunity to test a population during (or after) selective pressure to adapt to a freshwater existence. No evidence of the hemoglobin polymorphism was found, indeed some doubt was cast upon the European work due to technique aberrations. The muscle myogen polymorphism was present in a few populations, however, no basic environmental pattern emerged. The possibility of these alleles being selectively neutral is discussed. Electrophoretic patterns of the hemoglobin and muscle myogen patterns provoked the suggestion that the various forms of stickleback do indeed belong to a single species. The pattern of the muscle myogen polymorphism (creatine kinase) was found to be inconsistent with the dimeric structure generally reported for the enzyme. The hypothesis relating the polymorphisms to anadromous existences must be rejected. Several alternative projects are suggested.

Text

2010-02-24

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http://hdl.handle.net/2429/20838

Zoology

University of British Columbia

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