Abstract Batrachochytrium dendrobatidis (Bd), a fungal pathogen that causes amphibian chytridiomycosis, has been implicated in population declines globally. To better understand how Bd affects survival and how threats vary spatially and temporally, we conducted long-term (range: 9–13 yrs) capture-recapture studies of boreal toads (Anaxyrus boreas) from three similar communities in western Montana. We also estimated temporal and spatial variation in population-level Bd prevalence among populations and the potential role of co-occurring Columbia spotted frogs (Rana luteiventris) in driving infection dynamics. Hierarchical models that accounted for detection uncertainty revealed Bd reduced apparent survival in one population that declined, was unassociated with survival in one stationary population, and was associated with increased survival in one population that is near extirpation. Despite different effects of Bd on hosts, pathogen prevalence was similar and synchronous across the populations separated by 111–176 km. Variation in Bd prevalence was driven partly by seasonal temperatures, but opposite the direction expected. Bd prevalence also decreased sharply over time across all populations, unrelated to trends in temperature, boreal toad survival, or infection dynamics of co-occurring Columbia spotted frogs. Toad Bd prevalence increased when frog abundance was high, consistent with an amplification effect. However, Bd prevalence of toads decreased as Bd prevalence of spotted frogs increased, consistent with a dilution effect. Our results reveal surprising variation in responses to Bd and show pathogen prevalence is not predictive of survival or population risk, and they illustrate the complexity in understanding disease dynamics across multiple populations.

中文翻译：

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对比蟾蜍种群对区域同步病原体（Batrachochytrium dendrobatidis）动态的人口学反应

摘要 Batrachochytrium dendrobatidis (Bd) 是一种引起两栖动物壶菌病的真菌病原体，与全球人口下降有关。为了更好地了解 Bd 如何影响生存以及威胁如何在空间和时间上变化，我们对来自蒙大拿州西部三个类似社区的北方蟾蜍 (Anaxyrus boreas) 进行了长期（范围：9-13 年）捕获-再捕获研究。我们还估计了种群间 Bd 流行率的时间和空间变化，以及共同发生的哥伦比亚斑蛙（Rana luteiventris）在驱动感染动态方面的潜在作用。考虑检测不确定性的分层模型显示 Bd 降低了一个下降种群的表观存活率，与一个静止种群的存活率无关，并且与一个接近灭绝的种群的存活率增加有关。尽管 Bd 对宿主的影响不同，但病原体流行在相距 111-176 公里的种群中相似且同步。Bd 流行率的变化部分是由季节性温度驱动的，但与预期的方向相反。随着时间的推移，所有种群的 Bd 流行率也急剧下降，这与温度趋势、北方蟾蜍的存活率或同时发生的哥伦比亚斑点蛙的感染动态无关。当青蛙丰度高时，蟾蜍 Bd 流行率增加，与放大效应一致。然而，蟾蜍的 Bd 流行率随着斑点青蛙 Bd 流行率的增加而下降，这与稀释效应一致。