1. State Key Laboratory of Vegetation and Environmental Change Institute of Botany, Chinese Academy of Sciences No. 20 Nanxincun, Xiangshan Beijing 100093 China
2. University of Chinese Academy of Sciences Beijing 100049 China
3. Department of Organismic and Evolutionary Biology Harvard University Cambridge MA 02138 USA
4. Department of Ecology, Evolution and Behavior University of Minnesota St Paul MN 55108 USA