1. Key Laboratory of Aquatic Botany and Watershed Ecology; Wuhan Botanical Garden; Chinese Academy of Sciences; Wuhan 430074 Hubei China
2. Department of Ecology and Evolutionary Biology; University of California; Los Angeles CA 90095-7239 USA
3. Biodiversity and Conservation Biology; Swiss Federal Research Institute WSL; Zürcherstrasse 111 CH-8903 Birmensdorf Switzerland
4. Faculty of Life and Environmental Sciences; University of Iceland; Sturlugata 7 101 Reykjavík Iceland
5. Institute of the Environment and Sustainability; University of California; Los Angeles CA 90095-1496 USA