Department of Evolutionary Biology and Environmental Studies, University of Zurich, Winterthurerstrasse 190, CH-8057, Zurich, Switzerland; Department of Biology, Aarhus University, Ny Munkegade 114-116, DK-8000, Aarhus, Denmark.
Department of Evolutionary Biology and Environmental Studies, University of Zurich, Winterthurerstrasse 190, CH-8057, Zurich, Switzerland.
J Therm Biol. 2023 Aug;116:103680. doi: 10.1016/j.jtherbio.2023.103680. Epub 2023 Aug 10.
Elevated temperatures are expected to rise beyond what the physiology of many organisms can tolerate. Behavioural responses facilitating microhabitat shifts may mitigate some of this increased thermal selection on physiology, but behaviours are themselves mediated by physiology, and any behavioural response may trade-off against other fitness-related activities. We investigated whether experimental evolution in different thermal regimes (Cold: 15 °C; Hot: 31 °C; Intergenerational fluctuation 15/31 °C; Control: 23 °C) resulted in genetic differentiation of standard locomotor activity in the dung fly Sepsis punctum. We assessed individual locomotor performance, an integral part of most behavioral repertoires, across eight warm temperatures from 24 °C to 45 °C using an automated device. We found no evidence for generalist-specialist trade-offs (i.e. changes in the breadth of the performance curve) for this trait. Instead, at the warmest assay temperatures hot-selected flies showed somewhat higher maximal performance than all other, especially cold-selected flies, overall more so in males than females. Yet, the flies' temperature optimum was not higher than that of the cold-selected flies, as expected under the 'hotter-is-better' hypothesis. Maximal locomotor performance merely weakly increased with body size. These results suggest that thermal performance curves are unlikely to evolve as an entity according to theory, and that locomotor activity is a trait of limited use in revealing thermal adaptation.
预计温度升高将超过许多生物的生理机能所能承受的范围。促进小生境转移的行为反应可能会减轻一些生理上的这种增加的热选择，但行为本身受到生理机能的调节，任何行为反应都可能与其他与健康相关的活动产生权衡。我们研究了在不同的热环境（冷：15°C；热：31°C；世代波动 15/31°C；对照：23°C）下进行的实验进化是否会导致粪蝇 Sepsis punctum 的标准运动活性产生遗传分化。我们使用自动化设备在 24°C 到 45°C 的八个温暖温度下评估了个体的运动表现，这是大多数行为组合的一个组成部分。我们没有发现这种特征存在一般专家权衡（即表现曲线的广度变化）的证据。相反，在最温暖的测定温度下，热选择的苍蝇表现出比所有其他苍蝇，特别是冷选择的苍蝇，更高的最大性能，雄性比雌性更为明显。然而，苍蝇的最佳温度并不高于冷选择的苍蝇，这与“越热越好”的假设相符。最大运动性能仅随体型微弱增加。这些结果表明，根据理论，热性能曲线不太可能作为一个整体进化，而运动活性是揭示热适应的有限用途的特征。
