Postglacial recolonization patterns and genetic relationships among whitefish (Coregonus sp.) populations in Denmark, inferred from mitochondrial DNAand microsatellite markers

The genetic relationships among morphologically and geographically divergen t populations of whitefish (genus: Coregonus) from Denmark and the Baltic S ea region were studied by analysis of microsatellites and polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis of mi tochondrial DNA (mtDNA) segments, The endangered North Sea houting (classif ied as C. oxyrhynchus) differs morphologically and physiologically from oth er Danish whitefish (C. lavaretus). However, limited divergence of North Se a houting was observed both at the level of mtDNA and microsatellites. The implications of these results for the conservation status of North Sea hout ing are discussed in the light of current definitions of evolutionary signi ficant units. Both mtDNA and microsatellite data indicated that postglacial recolonization by C. lavaretus in Denmark was less likely to have taken pl ace from the Baltic Sea. Instead, the data suggested a recent common origin of all Danish whitefish populations, including North Sea houting, probably by recolonization via the postglacial Elbe River system. Estimates of gene tic differentiation among populations based on mtDNA and microsatellites we re qualitatively different. In addition, for both classes of markers analys es of genetic differentiation yielded different results, depending on wheth er molecular distances between alleles or haplotypes were included.