PHYLOGEOGRAPHY AND POSTGLACIAL DISPERSAL OF ARCTIC CHARR SALVELINUS-ALPINUS IN NORTH-AMERICA

Restriction fragment length polymorphism analysis of mitochondrial DNA (mtDNA) was used to reconstruct postglacial dispersal routes of arcti c charr Salvelinus alpinus in North America. Twelve of 35 restriction enzymes detected polymorphisms among representative populations, revea ling two distinct lineages with an estimated nucleotide divergence of 1.32%. Subsequent screening of 869 fish from 54 populations with four diagnostic restriction enzymes showed that these lineages have largely allopatric distributions, suggesting their dispersal from separate no rthern and eastern glacial refugia. In addition, geographical and gene tic structure among eastern populations suggested the existence of a s econd eastern refuge. Among the three lineages, the most divergent (Ar ctic) lineage occurred from Alaska east to northern Labrador. Quebec, New Brunswick, and New England were colonized by a second (Laurentian) lineage, and Labrador by a third group. Contact between refugial grou ps was only detected in two Labrador populations. The Arctic lineage w as highly differentiated from eastern North American and European hapl otypes, and probably diverged during the early Pleistocene. By contras t, the Laurentian and Labrador groups were similar to Old World charr, suggesting a shared ancestry during the mid-pleistocene. In addition, the close relationship between Labrador and Laurentian charr indicate s their probable divergence during the Wisconsinan glaciation.