Data from: Evolutionary rescue and local adaptation under different rates of temperature increase: a combined analysis of changes in phenotype expression and genotype frequency in Paramecium microcosms

Evolutionary Rescue (ER) occurs when populations, which have declined due to rapid environmental change, recover through genetic adaptation. The success of this process and the evolutionary trajectory of the population strongly depend on the rate of environmental change. Here we investigated how different rates of temperature increase (from 23°C to 32°C) affect population persistence and evolutionary change in experimental microcosms of the protozoan Paramecium caudatum. Consistent with theory on ER, we found that those populations experiencing the slowest rate of temperature increase were the least likely to become extinct and tended to be the best adapted to the new temperature environment. All high-temperature populations were more tolerant to severe heat stress (35°C, 37°C), indicating a common mechanism of heat protection. High-temperature populations also had superior growth rates at optimum temperatures, leading to the absence of a pattern of local adaptation to control (23°C) and high-temperature (32°C) environments. However, high-temperature populations had reduced growth at low temperatures (5-9°C), causing a shift in the temperature niche. In part, the observed evolutionary change can be explained by selection from standing variation. Using mitochondrial markers, we found complete divergence between control and high-temperature populations in the frequencies of six initial founder genotypes. Our results confirm basic predictions of ER and illustrate how adaptation to an extreme local environment can produce positive as well as negative correlated responses to selection over the entire range of the ecological niche.

进化拯救（Evolutionary Rescue, ER）指的是，因环境剧变而发生数量衰减的种群，通过遗传适应实现种群恢复的过程。该过程的成败与种群的演化轨迹，高度依赖于环境变化的速率。本研究以原生动物尾草履虫（Paramecium caudatum）的实验微宇宙为模型，探究了不同升温速率（从23℃升至32℃）对种群存续与演化过程的影响。与进化拯救理论的预测一致，本研究发现升温速率最慢的种群灭绝概率最低，且往往最适应新的温度环境。所有高温处理种群均对极端热胁迫（35℃、37℃）具有更高的耐受性，这表明存在一套共通的热保护机制。高温处理种群在适宜温度下的生长速率也更优，这使得其未表现出对对照温度（23℃）与高温环境（32℃）的局部适应性分化。但高温处理种群在低温环境（5℃-9℃）下的生长能力出现下降，导致其温度生态位发生偏移。观测到的演化变化，部分可通过对现存遗传变异的选择作用得到解释。通过线粒体标记（mitochondrial markers）分析，我们发现对照种群与高温处理种群在6种初始奠基者基因型的频率上已出现完全分化。本研究结果验证了进化拯救理论的核心预测，并阐明了对极端局部环境的适应，如何在生态位的全范围内同时产生正向与负向的选择相关响应。