Berger David, Stångberg Josefine, Baur Julian, Walters Richard J
Department of Ecology and Genetics, Evolutionary Biology Centre, Uppsala University, Norbyvägen 18D, 75236 Uppsala, Sweden.
Centre for Environmental and Climate Research, Lund University, Sölvegatan 37, 223 62 Lund, Sweden.
Proc Biol Sci. 2021 Feb 10;288(1944):20203094. doi: 10.1098/rspb.2020.3094. Epub 2021 Feb 3.
Adaptation in new environments depends on the amount of genetic variation available for evolution, and the efficacy by which natural selection discriminates among this variation. However, whether some ecological factors reveal more genetic variation, or impose stronger selection pressures than others, is typically not known. Here, we apply the enzyme kinetic theory to show that rising global temperatures are predicted to intensify natural selection throughout the genome by increasing the effects of DNA sequence variation on protein stability. We test this prediction by (i) estimating temperature-dependent fitness effects of induced mutations in seed beetles adapted to ancestral or elevated temperature, and (ii) calculate 100 paired selection estimates on mutations in benign versus stressful environments from unicellular and multicellular organisms. Environmental stress did not increase mean selection on de novo mutation, suggesting that the cost of adaptation does not generally increase in new ecological settings 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 in fitness. These results have important implications for genetic diversity gradients and the rate and repeatability of evolution under climate change.
在新环境中的适应取决于可供进化的遗传变异量，以及自然选择区分这种变异的效力。然而，一些生态因素是否比其他因素揭示出更多的遗传变异，或施加更强的选择压力，通常并不清楚。在这里，我们应用酶动力学理论表明，预计全球气温上升将通过增加DNA序列变异对蛋白质稳定性的影响，强化全基因组的自然选择。我们通过以下方式检验这一预测：（i）估计适应祖先温度或升高温度的种子甲虫中诱导突变的温度依赖性适合度效应，以及（ii）计算来自单细胞和多细胞生物的良性与应激环境中突变的100对选择估计值。环境压力并未增加对新生突变的平均选择，这表明在生物体不适应的新生态环境中，适应成本通常不会增加。然而，温度升高增加了全基因组多态性的平均选择强度，这表现为适合度的突变负荷和突变方差均增加。这些结果对于遗传多样性梯度以及气候变化下进化的速率和可重复性具有重要意义。
