Data from: Local adaptation drives thermal tolerance among parasite populations: a common garden experiment

Understanding the evolutionary responses of organisms to thermal regimes is of prime importance to better predict their ability to cope with ongoing climate change. Although this question has attracted interest in free-living organisms, whether or not infectious diseases have evolved heterogeneous responses to climate is still an open question. Here, we ran a common garden experiment using the fish ectoparasite Tracheliastes polycolpus, (i) to test whether parasites living in thermally heterogeneous rivers respond differently to an experimental thermal gradient, and (ii) to determine the evolutionary processes (natural selection or genetic drift) underlying these responses. We demonstrated that the reaction norms involving the survival rate of the parasite larvae (i.e. the infective stage) across a temperature gradient significantly varied among six parasite populations. Using a Qst/Fst approach and phenotype-environment associations, we further showed that the evolution of survival rate partly depended upon temperature regimes experienced in situ, and was mostly underlined by diversifying selection, but also -to some extent- by stabilizing selection and genetic drift. This evolutionary response led to population divergences in thermal tolerance across the landscape, which has implications for predicting the effects of future climate change.

解析生物对热环境的演化响应，对于精准预测其应对当前气候变化的能力具有核心意义。尽管该议题在自由生活生物中已得到广泛关注，但寄生性病原对气候的演化响应是否存在异质性，仍是尚未解决的科学问题。本研究以鱼类外寄生虫*Tracheliastes polycolpus*为研究对象开展同质园实验（common garden experiment）：（1）验证栖息于热环境异质性河流中的寄生虫，对实验热梯度的响应是否存在种群间差异；（2）解析驱动这些响应的演化过程（自然选择（natural selection）或遗传漂变（genetic drift））。研究结果显示，六个寄生虫种群间，跨温度梯度的寄生虫幼虫（即感染阶段）存活率反应规范（reaction norms）存在显著差异。通过Qst/Fst分析法及表型-环境关联分析（phenotype-environment associations），本研究进一步发现，幼虫存活率的演化部分依赖于种群原位所经历的热环境，其主要由歧化选择（diversifying selection）驱动，同时在一定程度上也受到稳定选择（stabilizing selection）与遗传漂变的影响。这种演化响应使得不同种群间的热耐受性产生了地理分化，这一结果对未来气候变化影响的预测工作具有重要参考价值。