1. College of Life Sciences, Qinghai Normal University , Xining 810016 , China
2. Key Laboratory of Biodiversity Formation Mechanism and Comprehensive Utilization of the Qinghai-Tibet Plateau in Qinghai Province , Xining 810016 , China
3. State Key Laboratory of Tibetan Plateau Earth System, Resources and Environment, Institute of Tibetan Plateau Research , Beijing 100101 , China
4. Department of Ecology and Evolutionary Biology, University of Michigan , MI 48109 , USA