Genetic distinctiveness of endangered dwarf blue sheep (Pseudois nayaur schaeferi): evidence from mitochondrial control region and Y-linked ZFY intron sequences.

To elucidate the controversial systematic relationship of blue sheep (Pseudois nayaur) and endangered dwarf blue sheep, we sequenced part of the mtDNA control region and Y-linked ZFY intron, and carried out phylogenetic analyses. Mitochondrial results revealed that the dwarf blue sheep is a strongly supported monophyletic group, with an average of 12.21% sequence divergence from the blue sheep. This is the first genetic evidence for the distinctness of the dwarf blue sheep. ZFY intron results showed an average of 0.51% sequence divergence, and one shared haplotype between the dwarf blue sheep and blue sheep. By analyzing an expanded data set that incorporated ZFY intron sequences of two additional Ovis (sheep) species-O. nivicola and O. ammon--we demonstrated that ZFY intron provides good resolution at the species and genus levels. The ZFY intron sequence divergence between dwarf blue sheep and blue sheep was comparable to that within the two Ovis species. Moreover, we found intraspecific sequence variation in ZFY intron for all three species examined. We propose that dwarf blue sheep be designated as a subspecies of blue sheep, P. n. schaeferi.