1. USDA-ARS, Invasive Species and Pollinator Health Research Unit , 800 Buchanan Street, Albany, CA 94710 , USA
2. Department of Environmental Science Policy and Management, University of California , 137 Mulford Hall, Berkeley, CA 94720 , USA
3. Department of Natural Sciences and Mathematics, Dominican University of California , 50 Acacia Avenue, San Rafael, CA 94901 , USA