title: Large-scale recovery of an endangered amphibian despite ongoing exposure to multiple stressors.
abstract: Amphibians are one of the most threatened animal groups, with 32% of species at risk for extinction. Given this imperiled status, is the disappearance of a large fraction of the Earth's amphibians inevitable, or are some declining species more resilient than is generally assumed? We address this question in a species that is emblematic of many declining amphibians, the endangered Sierra Nevada yellow-legged frog (Rana sierrae). Based on >7,000 frog surveys conducted across Yosemite National Park over a 20-y period, we show that, after decades of decline and despite ongoing exposure to multiple stressors, including introduced fish, the recently emerged disease chytridiomycosis, and pesticides, R. sierrae abundance increased sevenfold during the study and at a rate of 11% per year. These increases occurred in hundreds of populations throughout Yosemite, providing a rare example of amphibian recovery at an ecologically relevant spatial scale. Results from a laboratory experiment indicate that these increases may be in part because of reduced frog susceptibility to chytridiomycosis. The disappearance of nonnative fish from numerous water bodies after cessation of stocking also contributed to the recovery. The large-scale increases in R. sierrae abundance that we document suggest that, when habitats are relatively intact and stressors are reduced in their importance by active management or species' adaptive responses, declines of some amphibians may be partially reversible, at least at a regional scale. Other studies conducted over similarly large temporal and spatial scales are critically needed to provide insight and generality about the reversibility of amphibian declines at a global scale.
authors.affiliation: Sierra Nevada Aquatic Research Laboratory, University of California, Mammoth Lakes, CA 93546; knapp@lifesci.ucsb.edu.
authors.forename: Roland A
authors.initials: RA
authors.lastname: Knapp
authors.affiliation: Western Ecological Research Center, US Geological Survey, Point Reyes National Seashore, CA 94956.
authors.forename: Gary M
authors.initials: GM
authors.lastname: Fellers
authors.affiliation: Western Ecological Research Center, US Geological Survey, Point Reyes National Seashore, CA 94956.
authors.forename: Patrick M
authors.initials: PM
authors.lastname: Kleeman
authors.affiliation: Department of Ecosystem Science and Management, Pennsylvania State University, University Park, PA 16802.
authors.forename: David A W
authors.initials: DA
authors.lastname: Miller
authors.affiliation: Department of Biology, San Francisco State University, San Francisco, CA 94132-1722.
authors.forename: Vance T
authors.identifier: 0000-0002-9682-1190
authors.initials: VT
authors.lastname: Vredenburg
authors.affiliation: Department of Environmental Science, Policy, and Management, University of California, Berkeley, CA 94720.
authors.forename: Erica Bree
authors.initials: EB
authors.lastname: Rosenblum
authors.affiliation: Department of Ecology, Evolution, and Marine Biology, University of California, Santa Barbara, CA 93106.
authors.forename: Cheryl J
authors.initials: CJ
authors.lastname: Briggs
mesh_terms: D000663:Amphibians; D000818:Animals; D002140:California; D003247:Conservation of Natural Resources; D017753:Ecosystem; D056727:Endangered Species; D004781:Environmental Exposure / Q000009:adverse effects; D005163:Factor Analysis, Statistical; D015233:Models, Statistical; D011156:Population Density; D011898:Ranidae; D062206:Spatial Analysis
keywords: Rana sierrae; Yosemite; amphibians; disease; recovery