Phylogeography of ground tit (Pseudopodoces humilis) based on mtDNA: evidence of past fragmentation on the Tibetan Plateau.

Pseudopodoces humilis, a long misclassified terrestrial tit, is the only species of parid whose distribution is limited to treeless terrain and endemic to the Tibetan Plateau. We revealed the phylogeographic structure of the species by using mitochondrial control region, as well as comparing morphological characters. The distinct geographic distributions of two major clades suggest spatial and temporal separations that coincide with important climatic and paleogeographic changes following the uplift of the Tibetan Plateau. Population expansion was inferred for the population at the platform of the Plateau 0.17 million years before present (Ma B.P.), and restricted gene flow with isolation by distance was detected within this region, congruent with expansion occurring after the extensive glacial period. A significant decrease in body size with decreasing altitude was found, possibly indicating selection for larger-sized birds at higher altitude.