Male reproductive effort might be evolving in the face of devastating disease in a threatened amphibian

The devastating infectious disease chytridiomycosis has caused declines of amphibians across the globe, yet some populations are persisting and even recovering. One understudied effect of wildlife disease is changes in reproductive effort. Here we aimed to understand if disease has plastic effects on reproduction and if reproductive effort could evolve with disease endemism. We compared the effects of experimental pathogen exposure (trait plasticity) and population-level disease history (evolution in trait baseline) on reproductive effort using gametogenesis as a proxy in the declining and endangered frog Litoria verreauxii alpina. We found that unexposed males from disease-endemic populations had higher reproductive effort, which is consistent with an evolutionary response to chytridiomycosis. We also found evidence of trait plasticity, where males and females were affected differently by infection: pathogen exposed males had higher reproductive effort (larger testes), whereas females had reduced reproductive effort (smaller and fewer developed eggs) regardless of the population of origin. Infectious disease can cause plastic changes in reproductive effort at an individual level, and population-level disease exposure can result in changes to baseline reproductive effort; therefore, individual- and population-level effects of disease should be considered when designing management and conservation programs for threatened and declining species. --

极具破坏性的传染性疾病壶菌病（chytridiomycosis）已在全球范围内引发两栖动物种群数量下降，但仍有部分种群得以存续甚至恢复。野生动物疾病尚未被充分研究的影响之一，是宿主繁殖投入的改变。本研究旨在探讨疾病是否会对繁殖产生表型可塑性效应，以及繁殖投入是否会随疾病的地方性流行而发生演化。本研究以配子发生作为繁殖投入的替代指标，在种群数量下降且处于濒危状态的韦氏雨滨蛙高山亚种（Litoria verreauxii alpina）中，对比了实验性病原体暴露（即性状可塑性）与种群水平的疾病暴露历史（即性状基线的演化）对繁殖投入的影响。研究发现，来自疾病地方性流行种群且未暴露于病原体的雄性个体，其繁殖投入更高，这与壶菌病驱动的演化响应相符。此外，本研究还发现了性状可塑性的相关证据：感染对雌雄个体的影响存在显著差异——暴露于病原体的雄性个体繁殖投入更高（睾丸更大），而雌性个体的繁殖投入则有所降低（发育中的卵子更小且数量更少），且该效应不受其来源种群的影响。传染性疾病可在个体层面引发繁殖投入的表型可塑性变化，而种群水平的疾病暴露也会导致繁殖投入基线发生改变；因此，在针对受威胁及种群下降物种制定管理与保护计划时，应同时考虑疾病在个体与种群两个层面的影响。