Phylogeographic structure, gene flow and species status in blue grouse (Dendragapus obscurus)

We investigated the genetic population structure and species status of a relatively sedentary bird that is a permanent resident of western North American forests, the blue grouse (Dendragapus obscurus). Phylogenetic analysis of complete mitochondrial control region DNA sequences resulted in the identification of three basal clades of haplotypes that were largely congruent with well-known biogeographical regions. These clades corresponded to the parapatric sooty (D. o. fuliginosus) and dusky (D. o. obscurus) subspecies groups of blue grouse plus a previously unrecognized division between northern and southern dusky grouse populations; the latter does not correspond closely to any currently recognized subspecies boundary. Approximately 66% of the total genetic variation was distributed among these three regions. Maximum likelihood estimates of gene flow between the regions were low or asymmetric; gene flow has been insufficient to prevent genetic divergence between dusky and sooty grouse. Estimates of gene flow among populations within sooty grouse were large except across the Columbia River valley. Among populations of dusky grouse, estimates of gene flow were heterogeneous and asymmetrical, reflecting large-scale fragmentation of the distribution due to landscape features and associated vegetation. Genetic, morphological and behavioural evidence suggest that sooty and dusky grouse are species-level taxa; the specific status of a third clade remains ambiguous.