Data from: Large-scale recovery of an endangered amphibian despite ongoing exposure to multiple stressors

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.

两栖动物是受威胁最为严重的动物类群之一，目前有32%的物种濒临灭绝风险。鉴于这一濒危现状，地球两栖动物的大规模消亡是否无可避免？抑或是部分种群衰退的物种具备比此前假设更强的恢复韧性？我们以一类极具代表性的衰退两栖动物——濒危的内华达山脉黄腿蛙（Rana sierrae）为研究对象，对该问题展开探讨。本研究基于20年间在优胜美地国家公园（Yosemite National Park）全境开展的逾7000次蛙类调查，结果显示：尽管经历了数十年的种群衰退，且持续受到多种胁迫因子的影响——包括外来鱼类、新出现的壶菌病（chytridiomycosis）以及农药——但内华达山脉黄腿蛙的种群数量在研究期间增长了7倍，年均增长率达11%。这类种群增长现象在优胜美地国家公园全境的数百个种群中均有出现，为在符合生态意义的空间尺度上实现两栖动物恢复提供了罕见案例。实验室控制实验的结果表明，这类种群增长或许部分源于该蛙对壶菌病的易感性降低。此外，在停止人工放养鱼群后，众多水域中的外来鱼类种群消失，这也为种群恢复提供了助力。我们记录到的内华达山脉黄腿蛙大规模种群增长现象表明：当栖息地相对完好，且通过主动管理或物种自身的适应性响应降低了胁迫因子的影响程度时，部分两栖动物的种群衰退或许可以实现部分逆转，至少在区域尺度上是可行的。当前亟需开展更多类似大时空尺度的研究，以在全球层面为两栖动物衰退的可逆性提供具有普适性的认知与理论支撑。