1. Universidad Nacional Autónoma de México (UNAM), Instituto de Ecología, Estación del Noroeste, Apartado Postal 1354, Hermosillo, Sonora, México 83000
2. Santa Monica Mountains National Recreation Area, 401 West Hillcrest Drive, Thousand Oaks, CA 91360, U.S.A.
3. University of California, Davis, Graduate Group in Ecology, 1 Shields Avenue, University of California, Davis, CA 95616, U.S.A.
4. University of California, Davis, Dept. Environmental Science and Policy, 1 Shields Avenue, University of California, Davis, CA 95616, U.S.A.