Mitochondrial DNA Variation among Anadromous Populations of Cisco (Coregonus artedii) as revealed by Restriction Analysis

Abstract

Mitochondrial DNA (mtDNA) restriction analyses were done to test the hypothesis that river populations of anadromous cisco from James-Hudson Bays that exhibit life-history variations are reproductively isolated. MtDNA variation among 141 cisco (Coregonus artedii) from eight rivers was studied with eight hexameric, four multihexameric and one multipentameric restriction enzymes which generated a mean of 78 fragments per fish. Pair-wise sequence divergence estimates among the 19 mtDNA clones resolved were generally low but highly variable (mean: 0.52%, range: 0.08 to 1.03%). UPGMA and Wagner parsimony analysis revealed two major clonal groups which differed in diversity and geographic distribution; the more diversified (nucleon diversity index; 0.70) and less diversified (0.31) groups were twice as abundant in James and Hudson Bays, respectively. This suggests that cisco of James-Hudson Bays are derived from two glacial refugia and that they recolonized the area by two major postglacial routes. The frequency distribution analysis of all defined clones revealed significant stock discreteness among Hudson Bay populations and a lack of population subdivision in James Bay. The genetic structuring and diversity of anadromous cisco in James-Hudson Bay is discussed in relation to historical biogeographical events and to interactions of various life-history stages with the physical oceanographic environment.