| Summary: | Genetic studies were undertaken to establish the bases of four electrophoretically polymorphic proteins in lake whitefish, Coregonus clupeaformis. These biochemical characters were then used to investigate zoogeographic problems in lake whitefish which had been posed as a result of morphological study by other workers. Breeding experiments revealed the genetics of the electrophoretic phenotypes of glycerol-3-phosphate dehydrogenase (G-3-PDH) isozymes from white muscle. The G-3-PDH isozyme phenotypes were explained on the basis of a molecular, genetic model involving two loci, one having two alleles and the second three alleles. This model predicted, through simple Mendelian non-dominance, a total of eighteen phenotypes, fifteen of which were observed among 2200 lake whitefish from 38 lakes in Western Canada. Additional genetic information was derived from examination of lake whitefish muscle for phenotypes of lactate dehydrogenase (LDH) produced by a heart-type LDH locus. This locus is represented by two alleles, the genetics of which were determined in an earlier study (Clayton and Franzin, 1970). Less precise information was obtained from study of malate dehydrogenase (MDH) and hemoglobin phenotypes. All biochemical data were used collectively to test an hypothesis, developed from morphological evidence, that lake whitefish existed in at least two refugia (Bering and Mississippi) during the Wisconsin glaciation, and that the variability seen among lake whitefish populations in Western Canada is at least partly due to postglacial admixture of two or more discrete stocks. The biochemical observations all revealed a break in gene frequencies at the periphery of the Yukon River watershed which is roughly consistent with morphological observations. Biochemical data suggest that gene flow in lake whitefish has been unidirectionally out of the Yukon River watershed.
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