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（thermal regimes）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重要性。尽管针对自由生活生物的相关研究已广受关注，但传染性病原生物是否会演化出对气候的异质性响应，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开展同质园实验（common garden experiment），旨在达成两项研究目标：其一，验证栖息于热环境异质性河流中的寄生虫，是否会对实验温度梯度产生差异化响应；其二，解析驱动此类响应的演化过程（自然选择或遗传漂变）。本研究证实，在6个寄生虫种群间，跨温度梯度的寄生虫幼虫（即感染阶段）存活率相关的反应规范（reaction norms）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，幼虫存活率的演化部分取决于其原生栖息地所经历的热环境，且该演化过程主要由歧化选择驱动，同时在一定程度上也受到稳定选择与遗传漂变的影响。这种演化响应使得不同种群间的热耐受性在景观尺度上产生了分化，这一结果对于预测未来气候变化的影响具有重要参考价值。