1. U.S. Geological Survey, Western Ecological Research Center, 505 Azuar Drive, Vallejo, CA 94592, USA.
2. Departments of Geography, Ecology and Evolutionary Biology, and Institute of the Environment and Sustainability, University of California, Los Angeles, Los Angeles, CA 90095–1524, USA.
3. U.S. Geological Survey, Patuxent Wildlife Research Center, 12100 Beech Forest Road, Laurel, MD 20708, USA.
4. Department of Environmental Health Sciences, University of California, Los Angeles, Los Angeles, CA 90095–1772, USA.
5. Department of Fisheries and Wildlife, Oregon State University, Corvallis, OR 97331, USA.
6. Smithsonian Environmental Research Center, P.O. Box 28, 647 Contees Wharf Road, Edgewater, MD 21037–0028, USA.
7. Department of Biology, Queen’s University, 116 Barrie Street, Kingston, Ontario K7L 3N6, Canada.