Phylogeography and population genetics of Schizothorax o’connori: strong subdivision in the Yarlung Tsangpo River inferred from mtDNA and microsatellite markers

The Qinghai-Tibet Plateau (QTP) is a biodiversity hotspot, resulting from its geological history, contemporary environment and isolation. Uplift of the QTP and Quaternary climatic oscillations are hypothesised to have influenced the genetic diversity, population structure and dynamics of all QTP endemic species. In this study, we tested this hypothesis by assaying variation at two mitochondrial DNA regions (cytochrome b and control region) and at 12 microsatellite loci of seven populations of the endemic fish, Schizothorax o'connori from the Yarlung Tsangpo River (YLTR) on the QTP. Analyses revealed one group of six populations to the west, above the Yarlung Tsangpo Grand Canyon (YTGC), and a second group to the east below the YTGC. Estimates of the timing of this east-west split indicate that these groups represent evolutionarily significant units that have evolved separately and rapidly in the middle Pleistocene, at the time of the Kunlun-Huanghe Movement A Phase and the Naynayxungla glaciation. Population dynamic analyses indicate that S. o'connori experienced a pronounced late Pleistocene expansion during the last interglacial period. The results of this study support the hypotheses that the QTP uplift and Quaternary climatic oscillations have played important roles in shaping the population genetics and dynamics of this endemic fish.