Data from: Microgeographic differentiation in thermal performance curves between rural and urban populations of an aquatic insect

The rapidly increasing rate of urbanization has a major impact on the ecology and evolution of species. While increased temperatures are a key aspect of urbanization (“urban heat islands”), we have very limited knowledge whether this generates differentiation in thermal responses between rural and urban populations. In a common garden experiment, we compared the thermal performance curves (TPCs) for growth rate and mortality in larvae of the damselfly Coenagrion puella from three urban and three rural populations. TPCs for growth rate shifted vertically, consistent with the faster-slower theoretical model whereby the cold-adapted rural larvae grew faster than the warm-adapted urban larvae across temperatures. In line with costs of rapid growth, rural larvae showed lower survival than urban larvae across temperatures. The relatively lower temperatures, hence expected shorter growing seasons in rural populations compared to the populations in the urban heat islands likely impose stronger time constraints to reach a certain developmental stage before winter, thereby selecting for faster growth rates. In addition, higher predation rates at higher temperature may have contributed to the growth rate differences between urban and rural ponds. A faster-slower differentiation in TPCs may be a widespread pattern along the urbanization gradient. The observed microgeographic differentiation in TPCs supports the view that urbanization may drive life history evolution. Moreover, because of the urban heat island effect, urban environments have the potential to aid in developing predictions on the impact of climate change on rural populations.快速推进的城市化进程对物种的生态与演化产生了显著影响。气温升高是城市化的核心特征之一，即“城市热岛（urban heat islands）”效应，但目前我们对其是否会引发城乡种群间热响应分化的认知仍十分有限。本研究通过同质园试验（common garden experiment），比较了来自3个城市种群与3个乡村种群的豆娘（Coenagrion puella）幼虫的生长率与死亡率热性能曲线（thermal performance curves，TPCs）。生长率的热性能曲线呈现垂直位移，契合“快-慢”理论模型：在所有温度梯度下，适应低温的乡村幼虫生长速度均快于适应高温的城市幼虫。与快速生长的代价相符，乡村幼虫在各温度下的存活率均低于城市幼虫。相较于城市热岛环境中的种群，乡村种群所处环境温度更低、生长季更短，这可能施加了更强的时间约束——迫使个体在冬季来临前完成特定发育阶段，进而筛选出更快的生长速率。此外，高温下更高的捕食压力或许也促成了城乡池塘间的生长率差异。热性能曲线的“快-慢”分化可能是沿城市化梯度广泛存在的模式。本研究观测到的微地理分化（microgeographic differentiation）现象，佐证了城市化可能推动生活史演化的观点。此外，依托城市热岛效应，城市环境或可帮助我们预测气候变化对乡村种群的影响。