Adaptation in new environments depends on the amount and type of genetic variation available for evolution, and the efficacy by which natural selection discriminates among this variation to favour the survival of the fittest. However, whether some environments systematically reveal more genetic variation in fitness, or impose stronger selection pressures than others, is typically not known. Here, we apply enzyme kinetic theory to show that rising global temperatures are predicted to intensify natural selection systematically throughout the genome by increasing the effects of DNA sequence variation on protein stability. We tested this prediction by i) estimating temperature-dependent fitness effects of induced random mutations in seed beetles adapted to ancestral or warm temperature, and ii) calculating 100 paired selection estimates on mutations in benign versus stressful environments from a diverse set of unicellular and multicellular organisms. Environmental stress per se did not increase the mean strength of selection on de novo mutation, suggesting that the cost of adaptation does not generally increase in new environments to which the organism is maladapted. However, elevated temperature increased the mean strength of selection on genome-wide polymorphism, signified by increases in both mutation load and mutational variance at elevated temperature. The theoretical predictions and empirical data suggest that this increase may correspond to a doubling of genome-wide selection for a predicted 2-4 degrees climate warming scenario in ectothermic organism living at temperatures close to their thermal optimum. These results have important implications for global patterns of genetic diversity and the rate and repeatability of evolution under climate change.

中文翻译：

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升高的温度增加了从头突变的全基因组选择

在新环境中的适应取决于可用于进化的遗传变异的数量和类型，以及自然选择可区分这种变异以促进优胜劣汰的能力。但是，通常尚不知道某些环境是否系统地揭示了适应性方面的更多遗传变异，还是施加了比其他环境更大的选择压力。在这里，我们应用酶动力学理论表明，升高的全球温度预计会通过增加DNA序列变异对蛋白质稳定性的影响而在整个基因组中系统地增强自然选择。我们通过以下方法测试了这一预测：i）估算适应于祖先或温暖温度的种子甲虫中诱导的随机突变的温度依赖性适应性效应，ii）计算来自各种单细胞和多细胞生物的良性与压力性环境中的突变的100个配对选择估计。环境压力本身并没有增加从头突变的平均选择强度，这表明适应的成本一般不会在有机体适应不良的新环境中增加。但是，高温增加了全基因组多态性选择的平均强度，这表明高温下突变量和突变方差的增加。理论预测和经验数据表明，对于生活在接近其热最适温度的外热生物，在预测的2-4度气候变暖情况下，这种增加可能对应于全基因组选择增加一倍。