1. Department of Ecology and Evolutionary Biology, University of California at Los Angeles, 621 Charles E. Young Drive South, Los Angeles, California 90095‐1606 USA
2. Biodiversity and Conservation Biology, Swiss Federal Research Institute for Forest, Snow and Landscape Research WSL, Zürcherstrasse 111, CH‐8903 Birmensdorf, Switzerland
3. Institute of the Environment, La Kretz Hall, Suite 300, 619 Charles E. Young Drive South, University of California, Los Angeles, CA 90095‐1496 USA