1. Ecology Graduate Group, University of California, 1 Shields Ave., Davis, California 95616 USA
2. Department of Environmental Science and Policy, University of California, 1 Shields Ave., Davis, California 95616 USA
3. Romberg Tiburon Center for Environmental Studies, San Francisco State University, San Francisco, California 94132 USA
4. Department of Entomology, University of California, 1 Shields Ave., Davis, California 95616 USA