Abstract Understanding why related species have differing population-level responses to threats can be key to identifying conservation options for declining populations. However, this is difficult when multiple threats are implicated. Chytrid fungus (Batrachochytrium dendrobatidis: Bd) is implicated in at least 500 amphibian population declines globally, although few tangible options exist to mitigate pathogen impacts. Other threatening processes also invariably operate on most amphibians. Non-native fish, for example, can contribute to amphibian declines and may exacerbate Bd impacts. We disentangled the impacts of Bd and non-native fish upon two stream breeding frog species with differing conservation statuses to reveal vital rates that are crucial for species persistence. Litoria spenceri are threatened and historically occurred at elevations between 300–1100 m asl in southeastern Australia. Litoria lesueurii are non-threatened and sympatric with L. spenceri at some sites. Using mark-recapture derived demographic rates known to correlate with climate and elevation, discrete-time deterministic population models were constructed for each species at high, moderate and low elevation sites, and multiple management scenarios. Our study reveals that age to maturation, clutch size and egg-year 1 survival influenced interspecific and intraspecific population-level responses of the two frogs to Bd impacts. Importantly, our results highlight that an amphibian population’s capacity to counteract Bd-mediated adult mortality is clearly constrained by other threats and environment interactions that moderate species recruitment. Furthermore, understanding limits to recruitment may help identify Bd mitigation strategies. In our study, disease mitigation may be best achieved at some sites by enhancing recruitment through non-native fish management.

中文翻译：

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标题：招募是了解两栖动物对壶菌感染的不同种群水平反应的关键

摘要 了解为什么相关物种对威胁有不同的种群水平反应可能是确定种群减少的保护方案的关键。但是，当涉及多个威胁时，这很困难。壶菌（Batrachochytrium dendrobatidis：Bd）与全球至少 500 种两栖动物数量下降有关，尽管几乎没有切实可行的选择可以减轻病原体的影响。其他威胁过程也总是对大多数两栖动物起作用。例如，非本地鱼类会导致两栖动物数量减少，并可能加剧 Bd 的影响。我们解开了 Bd 和非本地鱼类对两种具有不同保护状态的溪流繁殖青蛙物种的影响，以揭示对物种持久性至关重要的重要比率。Litoria spenceri 受到威胁，历史上发生在澳大利亚东南部海拔 300-1100 米之间的海拔。Litoria lesueurii 在某些地点不受威胁，与 L. spenceri 共存。使用已知与气候和海拔相关的标记重新捕获得出的人口统计率，为高、中和低海拔地点的每个物种以及多种管理方案构建了离散时间确定性种群模型。我们的研究表明，成熟年龄、离合器大小和第 1 年卵的存活率影响了两种青蛙对 Bd 影响的种间和种内种群水平反应。重要的是，我们的结果强调，两栖动物种群抵消 Bd 介导的成年死亡率的能力显然受到其他威胁和环境相互作用的限制，这些威胁和环境相互作用会缓和物种招募。此外，了解招聘的限制可能有助于确定 Bd 缓解策略。在我们的研究中，通过非本地鱼类管理加强招募，在某些地点可能最好地减轻疾病。