Insect pest control programs often use periods of insecticide treatment with intermittent breaks, to prevent fixing of mutations conferring insecticide resistance. Such mutations are typically costly in an insecticide-free environment, and their frequency is determined by the balance between insecticide treatment and cost of resistance. Ace, a key gene in neuronal signaling, is a prominent target of many insecticides and across several species, three amino acid replacements (I161V, G265A, and F330Y) provide resistance against several insecticides. Because temperature disturbs neuronal signaling homeostasis, we reasoned that the cost of insecticide resistance could be modulated by ambient temperature. Experimental evolution of a natural Drosophila simulans population at hot and cold temperature regimes uncovered a surprisingly strong effect of ambient temperature. In the cold temperature regime, the resistance mutations were strongly counter selected (s = − 0.055), but in a hot environment, the fitness costs of resistance mutations were reduced by almost 50% (s = − 0.031). We attribute this unexpected observation to the advantage of the reduced enzymatic activity of resistance mutations in hot environments. We show that fitness costs of insecticide resistance genes are temperature-dependent and suggest that the duration of insecticide-free periods need to be adjusted for different climatic regions to reflect these costs. We suggest that such environment-dependent fitness effects may be more common than previously assumed and pose a major challenge for modeling climate change.

中文翻译：

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Ace 杀虫剂抗性突变的适应性效应由环境温度决定

害虫控制计划经常使用间歇性的杀虫剂处理期，以防止固定赋予杀虫剂抗性的突变。这种突变在无杀虫剂的环境中通常代价高昂，其频率取决于杀虫剂处理和抗药性成本之间的平衡。Ace 是神经元信号传导中的关键基因，是许多杀虫剂的重要靶标，并且在多个物种中，三种氨基酸替代物（I161V、G265A 和 F330Y）提供了对几种杀虫剂的抗性。因为温度扰乱了神经元信号的稳态，我们推断杀虫剂抗性的成本可以通过环境温度来调节。在高温和低温条件下自然果蝇种群的实验进化揭示了环境温度的惊人强烈影响。在低温条件下，抗性突变被强烈反选择（s = - 0.055），但在炎热环境中，抗性突变的适应度成本降低了近 50％（s = - 0.031）。我们将这一出乎意料的观察归因于热环境中抗性突变的酶活性降低的优势。我们表明杀虫剂抗性基因的适应度成本与温度有关，并建议需要针对不同的气候区域调整无杀虫剂期的持续时间以反映这些成本。