Mitochondrial DNA patterns among endemic stickleback from the Queen Charlotte Islands: a preliminary survey

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Abstract
Mitochondrial DNA (mtDNA) restriction fragments were analyzed in 30 individuals from four populations of Gasterosteus aculeatus from the Queen Charlotte Islands, British Columbia. Two morphologically divergent endemic freshwater populations (Boulton Lake, Drizzle Lake), a typical stream form, and a brackish form were sampled. mtDNA size variation of 70 to 180 base pairs was noted among individuals from all populations, and 1.1 and 5.0 kilobase duplications were observed in mtDNAs from two individuals. Analysis of 75 mtDNA fragments produced by five restriction endonucleases revealed seven clones differing by less than 1.0% sequence divergence. While the high degree of genetic similarity is consistent with a postglacial origin of these populations, the presence of a unique restriction site among geographically isolated populations suggests that these endemics may have had a common freshwater ancestor that inhabited periglacial freshwater habitats rather than being independently derived from marine forms.