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.

探究生物对热环境条件的演化响应，对于精准预测其应对当前气候变化的能力至关重要。尽管该问题已在自由生活生物中得到广泛关注，但传染性疾病对气候的演化响应是否存在异质性，仍是一个尚未解决的科学问题。
本研究以鱼类体外寄生虫Tracheliastes polycolpus为研究对象，开展同质园实验（common garden experiment），旨在实现两大研究目标：其一，验证栖息于热环境异质性河流中的寄生虫，对实验温度梯度的响应是否存在差异；其二，解析驱动这些响应的演化过程，即自然选择（natural selection）或遗传漂变（genetic drift）。
研究结果表明，在六个寄生虫种群之间，寄生虫幼虫（即感染阶段（infective stage））在温度梯度下的存活率反应规范（reaction norm）存在显著差异。
通过Qst/Fst分析法（Qst/Fst approach）与表型-环境关联分析（phenotype-environment associations），本研究进一步发现，寄生虫存活率的演化部分取决于其原生栖息环境所经历的热环境条件，其驱动因素以歧化选择（diversifying selection）为主，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。
这种演化响应使得种群间的热耐受性在整个景观尺度上产生分化，这一发现对于预测未来气候变化的影响具有重要的参考价值。