A new perspective on amphibians under global change: Detecting sublethal effects of environmental stress as agents of silent population declines

两栖动物处于全球生物多样性危机的最前沿，这是由于与人类全球变化有关的干扰，如栖息地破坏，持续的城市化和农业扩张。但是，生物多样性也在不受这种直接干扰影响的栖息地中丧失，这可能是由化学污染，病原体和持续的气候变化等环境压力因素造成的，导致稳定但无声的人口下降。暴露于亚致死的环境压力会增加应激激素水平，但也可能影响形态学，生理学和免疫功能，对性能，健康和生存产生重要的遗留影响。在全球变化的现实中，两栖动物在所有生命阶段都暴露于同时发生的压力源，但调查压力源相互作用的研究很少，对两栖动物不同生命阶段的长期研究完全缺失，但需要估计亚致死环境压力对种群规模的影响。拟议的项目旨在阐明亚致死环境压力在两栖动物神秘衰退中的作用，并制定早期预警检测工具，如果人口已经长期强调，但尚未或隐性下降的非侵入性压力激素测量两栖动物繁殖池塘。特别是，该项目将通过分析形态学，生理学，内分泌学，免疫学和遗传生物标志物作为压力的适当代理，研究对热应力和硝酸盐污染的短期和长期反应。这项研究将集中在一个共同的，但缓慢下降的无尾类物种，共同的青蛙（蛙temporaria）。此外，本研究的目的是确定该物种的驯化潜力，以压力条件下，将有助于评估未来的威胁R。面对全球变化的时间。该研究基于三个连续的组成部分：（A）荟萃分析，研究水生污染物和温度对两栖动物的相互作用的经验知识，（B）为期三年的实地研究，重点是不同的硝酸盐污染对幼虫和成虫的应激激素水平的影响。（C）实验室研究，调查温度波动和硝酸盐污染对变态期间和之后的各种应激生物标志物的影响。这项研究的结果将使我们能够通过检测多种应激生物标志物来更全面地了解对不断变化的环境的应激反应，并将提供对全球变化的亚致死效应的见解，这些影响会不知不觉地影响两栖动物种群，从而导致衰退或适应。本研究结果可作为红腹锦鸡儿种群保护策略的依据。temporaria在其分布范围内急剧下降。

Amphibians are at the forefront of the worldwide biodiversity crisis due to disturbances associated with anthropogenic global change such as habitat destruction, ongoing urbanization, and agricultural expansion. But biodiversity is also lost in habitats unaffected by such direct disturbances, possibly caused by environmental stressors such as chemical pollution, pathogens, and ongoing climate change resulting in steady but silent population declines. Exposure to sublethal environmental stressors increases the stress-hormone level but might also affect morphology, physiology, and immune functioning with important carry-over effects to performance, health, and survival. In global change reality, amphibians at all life stages are exposed to simultaneously occurring stressors but studies investigating interactive effects of stressors are rare and long-term studies on various life stages of amphibians are completely missing but needed to estimate sublethal stress effects on population scale.The proposed project aims to clarify the role of sublethal environmental stressors in enigmatic amphibian declines and to develop an early warning tool for detecting if populations are already chronically stressed but not yet or insidiously declining by noninvasive stress-hormone measurements in amphibian breeding ponds. In particular, this project will investigate short- and long-term responses to thermal stress and nitrate pollution by analyzing morphological, physiological, endocrinological, immunological, and genetic biomarkers as suitable proxies for stress. The study will focus on a common, but slowly declining anuran species, the common frog (Rana temporaria). Also, this study aims to determine the acclimation potential of this species to stressful conditions and will help to assess the future threat of R. temporaria in the face of global change. The study is based on three consecutive components: (A) a meta-analysis, studying the empirical knowledge on the interactive effects of aquatic contaminants and temperature on amphibians, (B) a field study over three years, focusing on the impact of different nitrate contaminations on stress-hormone levels in larval and adult R. temporaria, and (C) a laboratory study, investigating the effects of temperature fluctuations and nitrate pollution on various biomarkers of stress during and after metamorphosis. The results of this study will enable us to understand stress responses to changing environments more holistically by detecting multiple biomarkers of stress and will provide insights into sublethal effects of global change which affect amphibian populations insidiously resulting in either decline or adaptation. Further, the results of this study might serve as a basis for appropriate conservation strategies before populations of R. temporaria proceed to decline dramatically across its distribution range.