Aquatic insect growth is tightly linked to environmental temperature. Growth rate tends to increase with rising temperatures. Growth rate integrates different factors related to population fitness, being partly responsible for species distribution. We aim to estimate daily growth rates from mayfly nymphs reared under different thermal regimes in the field, during five different periods from 2016 to 2018. Twelve species of mayflies were reared in mesocosms in six streams (from three altitudinal levels with a mean elevation 725, 1069, and 1509 m.a.s.l.). Additionally, we transplanted nymphs between lowest and highest pairs of streams, thus rearing them under a different thermal regime. Temperature and other ambient variables were recorded at regular intervals. Daily growth rate (dgr) of most species resulted lower in the higher pair of streams (colder sites) than in the medium and lower streams (warmer sites). Transplant experiment also clearly showed this tendency: (1) nymphs transplanted to colder thermal regimes grew slower than those reared under their natural (warmer) regime and (2) nymphs transplanted to hotter thermal regimes grew faster than those reared under their original (colder) regime. Nymphs of three species (Americabaetis alphus, Leptohyphes eximius, and Cloeodes penai) did not show differences in growth among treatments. Our findings relating sensitiveness of Ephemeroptera nymphs to small temperature changes suggest that the distribution of some species will modify by increases in temperature derived from climatic change.

中文翻译：

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在不同温度下，田间饲养的蜉蝣（蜉蝣）的生长速度不同

水生昆虫的生长与环境温度密切相关。随着温度的升高，生长速度趋于加快。增长率综合了与种群适应度相关的不同因素，对物种分布负有部分责任。我们的目标是估计 2016 年至 2018 年五个不同时期在田间不同温度条件下饲养的蜉蝣若虫的日增长率。 十二种蜉蝣被饲养在六条溪流（来自三个海拔高度，平均海拔 725， 1069 和 1509 masl）。此外，我们在最低和最高的溪流对之间移植了若虫，从而在不同的温度条件下饲养它们。定期记录温度和其他环境变量。大多数物种的日增长率 (dgr) 在较高的溪流对（较冷的地点）中低于中流和较低的溪流（较暖的地点）。移植实验也清楚地表明了这种趋势：（1）移植到较冷热环境下的若虫比在自然（较暖）环境下饲养的若虫生长得慢；（2）移植到较热热环境下的若虫比在原始（较冷）环境下饲养的若虫生长得更快政权。三种若虫（Americabaetis alphus、Leptohyphes eximius和Cloeodes penai ) 在处理之间没有表现出生长差异。我们将蜉蝣若虫对小温度变化的敏感性的研究结果表明，某些物种的分布将因气候变化引起的温度升高而改变。