Data from: Larval environment alters amphibian immune defenses differentially across life stages and populations

Recent global declines, extirpations and extinctions of wildlife caused by newly emergent diseases highlight the need to improve our knowledge of common environmental factors that affect the strength of immune defense traits. To achieve this goal, we examined the influence of acidification and shading of the larval environment on amphibian skin-associated innate immune defense traits, pre and post-metamorphosis, across two populations of American Bullfrogs (Rana catesbeiana), a species known for its wide-ranging environmental tolerance and introduced global distribution. We assessed treatment effects on 1) skin-associated microbial communities and 2) post-metamorphic antimicrobial peptide (AMP) production and 3) AMP bioactivity against the fungal pathogen Batrachochytrium dendrobatidis (Bd). While habitat acidification did not affect survival, time to metamorphosis or juvenile mass, we found that a change in average pH from 7 to 6 caused a significant shift in the larval skin microbial community, an effect which disappeared after metamorphosis. Additionally, we found shifts in skin-associated microbial communities across life stages suggesting they are affected by the physiological or ecological changes associated with amphibian metamorphosis. Moreover, we found that post-metamorphic AMP production and bioactivity were significantly affected by the interactions between pH and shade treatments and interactive effects differed across populations. In contrast, there were no significant interactions between treatments on post-metamorphic microbial community structure suggesting that variation in AMPs did not affect microbial community structure within our study. Our findings indicate that commonly encountered variation in the larval environment (i.e. pond pH and degree of shading) can have both immediate and long-term effects on the amphibian innate immune defense traits. Our work suggests that the susceptibility of amphibians to emerging diseases could be related to variability in the larval environment and calls for research into the relative influence of potentially less benign anthropogenic environmental changes on innate immune defense traits.近年来，由新发传染病引发的全球野生动物种群衰退、局部灭绝与物种绝灭现象，凸显了深化对影响免疫防御性状强度的常见环境因子研究的必要性。为达成这一研究目标，我们以环境耐受范围广泛且已在全球广泛引种的美洲牛蛙（American Bullfrogs, *Rana catesbeiana*）的两个种群为研究对象，探究了幼体环境酸化与遮阴对其变态前、变态后皮肤相关先天免疫防御性状的影响。我们针对三项指标评估了不同处理的效应：1）皮肤相关微生物群落；2）变态后个体的抗菌肽（Antimicrobial Peptide, AMP）产生量；3）抗菌肽对真菌病原体蛙壶菌（Batrachochytrium dendrobatidis, Bd）的生物活性。尽管栖息地酸化对幼体存活率、变态时间以及幼蛙体重均无显著影响，但我们发现，水体平均pH由7降至6会显著改变幼体的皮肤微生物群落结构，且该效应在变态后消失。此外，我们还发现不同生命阶段的皮肤微生物群落结构存在显著差异，这表明两栖动物的皮肤微生物群落会受到变态相关的生理或生态变化的影响。进一步研究发现，变态后个体的抗菌肽产生量与生物活性，显著受到pH与遮阴处理的交互作用影响，且该交互效应在不同牛蛙种群间存在差异。与之相反，本研究中两种处理对变态后个体的皮肤微生物群落结构并无显著交互作用，这表明在本实验条件下，抗菌肽的变异并未对微生物群落结构产生影响。本研究结果表明，幼体环境中常见的环境变异（即池塘pH与遮阴程度），可对两栖动物的先天免疫防御性状产生即时与长期的双重影响。本研究提示，两栖动物对新发传染病的易感性可能与幼体环境的异质性相关，同时呼吁学界开展更多关于潜在危害更大的人为环境变化对先天免疫防御性状相对影响的研究。