A fundamental gap in climate change vulnerability research is an understanding of the relative thermal sensitivity of ectotherms. Aquatic insects are vital to stream ecosystem function and biodiversity but insufficiently studied with respect to their thermal physiology. With global temperatures rising at an unprecedented rate, it is imperative that we know how aquatic insects respond to increasing temperature and whether these responses vary among taxa, latitudes, and elevations. We evaluated the thermal sensitivity of standard metabolic rate in stream-dwelling baetid mayflies and perlid stoneflies across a ~2,000 m elevation gradient in the temperate Rocky Mountains in Colorado, U.S.A., and the tropical Andes in Napo, Ecuador. We used temperature-controlled water baths and microrespirometry to estimate changes in oxygen consumption. Tropical mayflies generally exhibited greater thermal sensitivity in metabolism compared to temperate mayflies; tropical mayfly metabolic rates increased more rapidly with temperature and the insects more frequently exhibited behavioral signs of thermal stress. By contrast, temperate and tropical stoneflies did not clearly differ. Varied responses to temperature among baetid mayflies and perlid stoneflies may reflect differences in evolutionary history or ecological roles as herbivores and predators, respectively. Our results show that there is physiological variation across elevations and species and that low elevation tropical mayflies may be especially imperiled by climate warming. Given such variation among species, broad generalizations about the vulnerability of tropical ectotherms should be made more cautiously.

中文翻译：

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热带和温带水生昆虫新陈代谢速率的温度依赖性：支持五花蝇而不是石蝇的气候变化假说。

气候变化脆弱性研究的根本缺陷是对等温线相对热敏性的理解。水生昆虫对维持生态系统功能和生物多样性至关重要，但对它们的热生理学研究不足。随着全球温度以前所未有的速度上升，当务之急是我们必须知道水生昆虫如何对温度升高做出反应，以及这些反应是否在分类，纬度和海拔之间变化。我们评估了在美国科罗拉多州的温带落基山脉和厄瓜多尔那坡的热带安第斯山脉中，栖于河床的甲虫和蠕动石蝇在约2,000 m的海拔梯度上对标准代谢率的热敏感性。我们使用温度控制的水浴和微呼吸测定法来估计氧气消耗量的变化。与温带may相比，热带may通常在代谢中表现出更高的热敏感性。热带may的代谢率随着温度的增加而迅速增加，而昆虫更频繁地表现出热应激的行为迹象。相比之下，温带和热带石蝇并没有明显区别。甲虫和蠕虫对温度的不同反应可能分别反映了进化史或作为食草动物和捕食者的生态作用的差异。我们的研究结果表明，海拔和物种之间存在生理差异，并且气候变暖可能会特别不利于低海拔热带梅花。考虑到物种之间的这种差异，应更加谨慎地对热带外热的脆弱性进行广泛的概括。