Data from: Host-pathogen metapopulation dynamics suggest high elevation refugia for boreal toads

Emerging infectious diseases are an increasingly common threat to wildlife. Chytridiomycosis, caused by the fungal pathogen Batrachochytrium dendrobatidis (Bd), is an emerging infectious disease that has been linked to amphibian declines around the world. Few studies exist that explore amphibian-Bd dynamics at the landscape scale, limiting our ability to identify which factors are associated with variation in population susceptibility and to develop effective in situ disease management. Declines of boreal toads (Anaxyrus boreas boreas) in the Southern Rocky Mountains are largely attributed to chytridiomycosis but variation exists in local extinction of boreal toads across this metapopulation. Using a large-scale historic dataset, we explored several potential factors influencing disease dynamics in the boreal toad-Bd system: geographic isolation of populations, amphibian community richness, elevational differences, and habitat permanence. We found evidence that boreal toad extinction risk was lowest at high elevations where temperatures may be sub-optimal for Bd growth and where small boreal toad populations may be below the threshold needed for efficient pathogen transmission. In addition, boreal toads were more likely to recolonize high elevation sites after local extinction, again suggesting that high elevations may provide refuge from disease for boreal toads. We illustrate a modeling framework that will be useful to natural resource managers striving to make decisions in amphibian-Bd systems. Our data suggest that in the southern Rocky Mountains high elevation sites should be prioritized for conservation initiatives like reintroductions.新发传染病正日益成为野生动物面临的普遍威胁。由蛙壶菌（Batrachochytrium dendrobatidis, Bd）引发的壶菌病（Chytridiomycosis）正是一类新发传染病，现已被证实与全球范围内两栖动物种群衰退紧密相关。目前鲜有研究在景观尺度上探讨两栖动物-蛙壶菌的互作动态，这限制了我们识别与种群易感性差异相关的影响因素，以及开发有效原位（in situ）疾病管理策略的能力。落基山脉南部的北美北方蟾蜍（Anaxyrus boreas boreas）种群衰退在很大程度上归因于壶菌病，但该集合种群（metapopulation）内各地的北美北方蟾蜍局域灭绝情况存在显著差异。本研究依托大规模历史数据集，探究了影响北美北方蟾蜍-蛙壶菌系统中疾病动态的多项潜在因素：种群地理隔离度、两栖动物群落丰富度、海拔差异以及生境持久性。研究结果显示，北美北方蟾蜍的局域灭绝风险在高海拔区域最低——这类区域的温度可能不适于蛙壶菌生长，且小型北美北方蟾蜍种群规模可能低于病原体高效传播所需的阈值。此外，北美北方蟾蜍在局域灭绝后更易重新定殖高海拔区域，这进一步表明高海拔区域可为北美北方蟾蜍提供疾病庇护所。本研究还展示了一套建模框架，可为致力于在两栖动物-蛙壶菌系统中制定决策的自然资源管理者提供实用支持。研究数据表明，在落基山脉南部，高海拔区域应被优先纳入再引入等保护行动的实施范畴。