Data from: Potential for adaptation to climate change: family-level variation in fitness-related traits and their responses to heat waves in a snail population

Background: On-going global climate change poses a serious threat for natural populations unless they are able to evolutionarily adapt to changing environmental conditions (e.g. increasing average temperatures, occurrence of extreme weather events). A prerequisite for evolutionary change is within-population heritable genetic variation in traits subject to selection. In relation to climate change, mainly phenological traits as well as heat and desiccation resistance have been examined for such variation. Therefore, it is important to investigate adaptive potential under climate change conditions across a broader range of traits. This is especially true for life-history traits and defences against natural enemies (e.g. parasites) since they influence organisms’ fitness both directly and through species interactions. We examined the adaptive potential of fitness-related traits and their responses to heat waves in a population of a freshwater snail, Lymnaea stagnalis. We estimated family-level variation and covariation in life history (size, reproduction) and constitutive immune defence traits [haemocyte concentration, phenoloxidase (PO)-like activity, antibacterial activity of haemolymph] in snails experimentally exposed to typical (15 °C) and heat wave (25 °C) temperatures. We also assessed variation in the reaction norms of these traits between the treatments. Results: We found that at the heat wave temperature, snails were larger and reproduced more, while their immune defence was reduced. Snails showed high family-level variation in all examined traits within both temperature treatments. The only negative genetic correlation (between reproduction and antibacterial activity) appeared at the high temperature. However, we found no family-level variation in the responses of most examined traits to the experimental heat wave (i.e. largely parallel reaction norms between the treatments). Only the reduction of PO-like activity when exposed to the high temperature showed family-level variation, suggesting that the cost of heat waves may be lower for some families and could evolve under selection. Conclusion: Our results suggest that there is genetic potential for adaptation within both thermal environments and that trait evolution may not be strongly affected by trade-offs between them. However, rare differences in thermal reaction norms across families indicate limited evolutionary potential in the responses of snails to changing temperatures during extreme weather events.

研究背景：当前持续的全球气候变化正对自然种群构成严重威胁，除非这些种群能够通过进化适应不断变化的环境条件（例如平均气温升高、极端天气事件频发）。进化改变的前提条件是，受选择作用的性状在种群内存在可遗传的遗传变异。针对气候变化的相关研究中，目前主要关注物候性状以及耐热、抗脱水能力这类性状的此类变异。因此，在更广泛的性状范围内探究气候变化条件下的适应潜力具有重要意义，这一点在生活史性状以及针对自然天敌（如寄生虫）的防御机制上尤为突出——因为这些性状既会直接影响生物的适合度，也会通过物种间的相互作用间接发挥作用。本研究以淡水椎实螺（*Lymnaea stagnalis*）的一个种群为对象，探究了与适合度相关的性状及其对热浪的响应的适应潜力。我们对实验暴露于典型温度（15℃）和热浪温度（25℃）下的螺类，估算了其生活史性状（体型大小、繁殖能力）以及组成型免疫防御性状[血淋巴细胞浓度、酚氧化酶（PO）样活性、血淋巴抗菌活性]的家系水平变异与协变关系。此外，我们还评估了这些性状在两种处理下的反应规范间的变异情况。研究结果：在热浪温度条件下，螺类体型更大、繁殖能力更强，但免疫防御能力有所下降。在两种温度处理下，所有检测性状均表现出较高的家系水平变异。仅在高温条件下出现了唯一的负遗传相关（繁殖能力与抗菌活性之间）。然而，我们未发现多数检测性状对实验热浪的响应存在家系水平变异（即两种处理间的反应规范大体平行）。仅高温暴露下酚氧化酶样活性的降低表现出家系水平变异，这表明热浪的适合度代价可能在部分家系中更低，且可在选择作用下发生进化。研究结论：我们的结果表明，在两种热环境下均存在适应所需的遗传潜力，且性状进化可能不会受到二者间权衡的强烈影响。不过，家系间热反应规范的少数差异表明，螺类在极端天气事件中应对温度变化的响应进化潜力有限。