Warmer nights offer no respite for a defensive mutualism

1. Ecologically-relevant symbioses are widespread in terrestrial arthropods but based on recent findings these specialized interactions are likely to be especially vulnerable to climate warming. Importantly, empirical data and climate models indicate that warming is occurring asynchronously, with nighttime temperatures increasing faster than daytime temperatures. Daytime (DTW) and nighttime warming (NTW) may impact ectothermic animals and their interactions differently as DTW results in greater daily temperature variation and moves organisms nearer to their thermal limits, while NTW avoids thermal limits and may relieve constraints of cooler nighttime temperatures; a nuance that has largely been ignored in the literature. 2. In laboratory experiments, we investigated how the timing of warming influences a widespread defensive mutualism involving the pea aphid, Acyrthosiphon pisum, and its heritable symbiont, Hamiltonella defensa, which protects against an important natural enemy, the pa...1. 生态相关共生（ecologically-relevant symbioses）在陆生节肢动物（terrestrial arthropods）中广泛分布，但最新研究表明，这类特化的种间互作极有可能对气候变暖尤为脆弱。值得注意的是，实证数据与气候模型均显示，变暖过程存在异步性：夜间气温的上升速率快于日间气温。日间增温（Daytime Warming, DTW）与夜间增温（Nighttime Warming, NTW）对变温动物（ectothermic animals）及其种间互作的影响存在显著差异：日间增温会加剧单日温度波动，使生物体更接近其热耐受极限；而夜间增温则不会触及热耐受极限，反而可能缓解夜间低温带来的生理约束——这一细微差异在现有学界研究中很大程度上被忽视了。 2. 在室内控制实验中，我们探究了增温时机如何影响一种广泛存在的防御性共生体系：该体系包含豌豆蚜（Acyrthosiphon pisum）及其可遗传共生菌——防御哈氏菌（Hamiltonella defensa），后者可帮助宿主抵御一类重要的天敌（原文末尾截断为"the pa..."）。