Acknowledgements
The research was supported by the Special Foundation for Basic Scientific and Technological Research Program (2013FY111800). We gratefully appreciate the help provided by the Administration of Wuliangushai Nature Reserve, the Administration of Wulagai Nature Reserve, the Administration of Khorchin Nature Reserve, the Administration of Dalinor Nature Reserve, the Administration of Chaganhu Nature Reserve, the Administration of Hengshuihu Nature Reserve and the Administration of Shahu Nature Reserve to access the study sites and provide facilitiesfor the surveys. Our thanks are especially to Dr. Wang Yuyu, Dr. Jiao Shengwu, Mr. Mo Xunqiang, Liu Yunzhu, Tao Cui, Chen Zhengrong, Qu Shang, Li Xiaojing, Tong Yuping, Li Yiyi, Zhu Yi, Yang Lingfan, Sun Gongqi, Li Gang and Jeroen Saccheri for assistance during the fieldwork; and to Li Yiyi for laboratory assistance and Li yu for assistance in part of data collection.