Geographic patterns in the genetic diversity of a northern sedge, Carex rariflora

We compared the genetic diversity of a northern wetland sedge, Carer rarifl ora, both within and between populations, in different habitat types, and a cross geographic regions with different glacial histories. Twelve populatio ns were sampled: 5 from each of two regions in northern Quebec, and 2 from northern Yukon. Habitat types were medium to rich fens, wet tidal flat, and alpine stream edge. Allele frequency data revealed a low degree of within- population genetic diversity (H-S = 0.07) and a high degree of genetic diff erentiation among populations (G(ST) = 0.47) compared with previously studi ed northern wetland Carer species. Higher genetic variability found in the Yukon than in Quebec could be explained by the presence of a glacial refugi um in much of Alaska and the Yukon throughout the Pleistocene. Low genetic diversity in Quebec suggests the occurrence of genetic bottlenecks resultin g from founder effects during postglacial colonization. There was a strong positive correlation between geographic distance and genetic distance among populations, and the three geographic regions were genetically distinct fr om one another. Detrended correspondence analysis of vegetation data reveal ed clear differences among the three habitat types, but we found no signifi cant correlation between habitat differences and genetic distance.