Data from: Genome-wide set of SNPs reveals evidence for two glacial refugia and admixture from postglacial recolonization in an alpine ungulate

Past glaciation events have played a major role in shaping the genetic
diversity and distribution of wild sheep in North America. The advancement
of glaciers can isolate populations in ice-free refugia, where they can
survive until the recession of ice sheets. The major Beringian refugium is
thought to have held thinhorn sheep (Ovis dalli) populations during times
of glacial advance. While isolation in the major refugium can account for
much of the genetic and morphological diversity seen in extant thinhorn
sheep populations, mounting evidence suggests the persistence of
populations in smaller minor refugia. We investigated the refugial origins
of thinhorn sheep using ~10 000 SNPs obtained via a cross-species
application of the domestic sheep ovine HD BeadChip to genotype 52
thinhorn sheep and five bighorn sheep (O. canadensis) samples.
Phylogenetic inference revealed a distinct lineage of thinhorn sheep
inhabiting British Columbia, which is consistent with the survival of a
group of thinhorn sheep in a minor refugium separate from the Beringian
refugium. Isolation in separate glacial refugia probably mediated the
evolution of the two thinhorn sheep subspecies, the white Dall's
sheep (O. d. dalli), which persisted in Beringia, and the dark
Stone's sheep (O. d. stonei), which utilized the minor refugium. We
also found the first genetic evidence for admixture between sheep from
different glacial refugia in south-central Yukon as a consequence of post
glacial expansion and recolonization. These results show that glaciation
events can have a major role in the evolution of species inhabiting
previously glaciated habitats and the need to look beyond established
refugia when examining the evolutionary history of such species.