Climate change is altering temperature means and variation, and both need to be considered in predictions underpinning conservation. However, there is no consensus in the literature regarding the effects of temperature fluctuations on biological functions. Fluctuations may affect biological responses because of inequalities from non‐linear responses, endocrine regulation or exposure to damaging temperatures. Here we establish the current state of knowledge of how temperature fluctuations impact biological responses within individuals and populations compared to constant temperatures with the same mean. We conducted a meta‐analysis of 143 studies on ectothermic animals (1492 effect sizes, 118 species). In this study, 89% of effect sizes were derived from diel cycles, but there were no significant differences between diel cycles and shorter (<8 h) or longer (>48 h) cycles in their effect on biological responses. We show that temperature fluctuations have little effect overall on trait mean and variance. Nonetheless, temperature fluctuations can be stressful: fluctuations increased ‘gene expression’ in aquatic animals, which was driven mainly by increased hsp70. Fluctuating temperatures also decreased longevity, and increased amplitudes had negative effects on population responses in aquatic organisms. We conclude that mean temperatures and extreme events such as heat waves are important to consider, but regular (particularly diel) temperature fluctuations are less so.

中文翻译：

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温度变化对变温动物生物反应的影响——荟萃分析


气候变化正在改变温度平均值和变化，在支持保护的预测中需要考虑这两者。然而，关于温度波动对生物功能的影响，文献中没有达成共识。波动可能会影响生物反应，因为非线性反应、内分泌调节或暴露于有害温度的不平等性。在这里，我们确定了温度波动如何影响个体和种群内部生物反应的知识现状，与具有相同平均值的恒定温度相比。我们对 143 项变温动物研究 （1492 个效应量，118 个物种） 进行了荟萃分析。在这项研究中，89% 的效应量来自 diel 循环，但 diel 循环与较短 （<8 h） 或较长 （>48 h） 循环对生物反应的影响没有显著差异。我们表明，温度波动总体上对性状均值和方差影响不大。尽管如此，温度波动可能会带来压力：波动会增加水生动物的“基因表达”，这主要是由 hsp70 的增加驱动的。温度波动也会缩短寿命，而振幅增加对水生生物的种群反应有负面影响。我们得出的结论是，平均温度和热浪等极端事件很重要，但常规（尤其是 diel）温度波动则不那么重要。