Tüzün Nedim, Stoks Robby
Evolutionary Stress Ecology and Ecotoxicology University of Leuven Leuven Belgium.
Evol Appl. 2020 Jul 9;14(1):24-35. doi: 10.1111/eva.13041. eCollection 2021 Jan.
There is mounting evidence that the widespread phenotypic changes in response to urbanization may reflect adaptations caused by rapid evolutionary processes driven by urban-related stressors. Compared to increased habitat fragmentation and pollution, adaptations towards another typical urban-related stressor, that is higher and longer lasting very high temperatures (heat waves), are much less studied. Notably, the sensitivities to heat waves of life-history traits and important fitness-related physiological traits such as immune responsiveness and bioenergetic variables (energy availability, energy consumption and their balance) have never been contrasted between urban and rural populations. By conducting a laboratory common-garden experiment, we compared effects of a simulated heat wave on life history (survival and growth rate), immune responsiveness and bioenergetic variables between three urban and three rural populations of the damselfly . Because energy-mediated trade-off patterns may only be detected under energetically costly manipulations, all larvae were immune-challenged by simulating ectoparasitism by water mites. As expected, the simulated heat wave caused negative effects on nearly all response variables. The immune responsiveness, on the other hand, increased under the heat wave, consistent with a trade-off pattern between immune function and growth, and this similarly between urban and rural populations. A key finding was that urban larvae suffered less from the simulated heat wave compared to the rural larvae in terms of a lower heat wave-induced depletion in energy availability. This suggests an adaptation of urban populations to better cope with the stronger and more frequent heat waves in cities. Notably, this urbanization-driven evolution in the bioenergetic variables was not apparent in the absence of a heat wave. Given that changes in energy budgets have strong fitness consequences, our findings suggest that the evolved higher ability to cope with heat waves is fundamental for the survival of urban damselfly populations.
越来越多的证据表明，城市化引发的广泛表型变化可能反映了由城市相关压力源驱动的快速进化过程所导致的适应性变化。与栖息地破碎化加剧和污染增加相比，针对另一种典型的城市相关压力源，即更高且持续时间更长的极高温度（热浪）的适应性研究要少得多。值得注意的是，城市和农村种群在生活史特征以及与重要适应性相关的生理特征（如免疫反应性和生物能量变量（能量可用性、能量消耗及其平衡））对热浪的敏感性方面从未进行过对比。通过开展一项实验室共同培养实验，我们比较了模拟热浪对豆娘三个城市种群和三个农村种群的生活史（存活率和生长率）、免疫反应性和生物能量变量的影响。由于能量介导的权衡模式可能仅在能量消耗高昂的操作下才能检测到，所有幼虫都通过模拟水螨的体外寄生进行免疫挑战。正如预期的那样，模拟热浪对几乎所有响应变量都产生了负面影响。另一方面，免疫反应性在热浪下有所增加，这与免疫功能和生长之间的权衡模式一致，城市和农村种群的情况类似。一个关键发现是，与农村幼虫相比，城市幼虫在模拟热浪中遭受的影响较小，因为热浪导致的能量可用性消耗较低。这表明城市种群具有更好应对城市中更强、更频繁热浪的适应性。值得注意的是，在没有热浪的情况下，这种由城市化驱动的生物能量变量进化并不明显。鉴于能量预算的变化对适应性有重大影响，我们的研究结果表明，进化出的更高应对热浪的能力是城市豆娘种群生存的基础。
