Am Nat. 2020 Jul;196(1):45-56. doi: 10.1086/709010. Epub 2020 May 27.
Activity times structure the thermal environments experienced by organisms. In mammals, species shift from being nocturnal to diurnal and vice versa, but the thermal consequences of variable activity patterns remain largely unexplored. Here we used theoretical thermoregulatory polygons bounded by estimates of basal metabolic rates (BMR), maximum metabolic rates (MMR), and thermal conductance () in small mammals to explore the metabolic consequences of exposure to global-scale daytime and nighttime temperatures. Model predictions indicated higher metabolic scope for activity for nocturnal species at low latitudes and that reduced minimum and larger body size increased the geographic range in which nocturnality was advantageous. Consistent with predictions, within rodents nocturnal species have low . However, nocturnal mammals tend to be smaller than diurnal species, likely reflecting the importance of additional factors driving body size. Projections of warming impacts on small mammals suggest that diurnal species could lose habitable space globally. Conversely, warming could lift cool temperature constraints on nocturnal species and increase habitable space, suggesting that a shift toward nocturnal niches might be favored in a warming world. Taken together, these findings demonstrate the importance of energetic considerations for endotherms in managing global change impacts on nocturnal and diurnal species.
活动时间塑造了生物体所经历的热环境。在哺乳动物中，物种从夜间活动转变为日间活动，反之亦然，但活动模式变化的热后果在很大程度上仍未得到探索。在这里，我们使用理论热调节多边形来探索暴露于全球范围的日间和夜间温度对小型哺乳动物的代谢后果，这些多边形由基础代谢率（BMR）、最大代谢率（MMR）和热导（）的估计值来界定。模型预测表明，在低纬度地区，夜间活动的物种在活动时具有更高的代谢范围，而最小热导的降低和体型的增大增加了夜间活动有利的地理范围。与预测一致，在啮齿动物中，夜间活动的物种具有较低的 。然而，夜间活动的哺乳动物往往比日间活动的物种小，这可能反映了驱动体型的其他因素的重要性。对小型哺乳动物变暖影响的预测表明，日间活动的物种可能会在全球范围内失去适宜生存的空间。相反，变暖可能会减轻夜间活动物种对低温的限制，并增加适宜生存的空间，这表明在变暖的世界中，向夜间生态位的转变可能更受青睐。综上所述，这些发现表明，对于恒温动物来说，能量因素在管理全球变化对夜间和日间物种的影响方面非常重要。
