Comparative phylogeography and evolutionary history of schizothoracine fishes in the Changtang Plateau and their implications for the lake level and Pleistocene climate fluctuations.

The water level oscillation of endorheic lakes and extent change of glaciers associated with the Asian monsoon are known as prominent representatives of climatic and environmental events in the Tibetan Plateau during the Quaternary. However, details process in spatial and temporal changes are still debated. We use the schizothoracines as a palaeoclimatic proxy to test two hypotheses concerning the evolution of Quaternary glaciations and lakes of the Changtang Plateau: (1) the Tibetan glaciations generally tended to decrease since the middle Pleistocene; (2) the lakes expansion was driven by summer monsoon rainfall. Based on a wide range-wide sampling throughout in the Changtang Plateau and its adjacent drainages, we constructed phylogeny and demographic histories of schizothoracines in the Changtang Plateau. Our results showed that the populations of the exorheic rivers and lakes in southern Tibet possessed higher genetic variability, earlier coalescent and expansion times than those of the endorheic lakes in the Changtang Plateau. Population expansions are highly consistent with phases of strong summer monsoon and high lake level during interglacial stages. The maximum growth rate intervals showed three pulses from 64.7 to 54.8, 39.6 to 31.0, and 14.9 to 2.4 kya respectively. The significant positive correlations were found between regional precipitation and genetic diversity, as well as coalescence time of populations in the endorheic lakes. We suggested that the demographic history of the schizothoracines reflects the spatial and temporal changes in climate and lake level, in particular, in regional precipitation gradients associated with changes of the South Asian monsoon, and supports the climatic hypothesis of a general diminishing tend in Tibetan glaciations in the Tibetan Plateau since the middle Pleistocene.