Institute of Evolutionary Biology and Environmental Studies, University of Zurich, 8057 Zurich, Switzerland.
Nature. 2011 Jun 2;474(7349):92-5. doi: 10.1038/nature10083.
Cryptic variation is caused by the robustness of phenotypes to mutations. Cryptic variation has no effect on phenotypes in a given genetic or environmental background, but it can have effects after mutations or environmental change. Because evolutionary adaptation by natural selection requires phenotypic variation, phenotypically revealed cryptic genetic variation may facilitate evolutionary adaptation. This is possible if the cryptic variation happens to be pre-adapted, or "exapted", to a new environment, and is thus advantageous once revealed. However, this facilitating role for cryptic variation has not been proven, partly because most pertinent work focuses on complex phenotypes of whole organisms whose genetic basis is incompletely understood. Here we show that populations of RNA enzymes with accumulated cryptic variation adapt more rapidly to a new substrate than a population without cryptic variation. A detailed analysis of our evolving RNA populations in genotype space shows that cryptic variation allows a population to explore new genotypes that become adaptive only in a new environment. Our observations show that cryptic variation contains new genotypes pre-adapted to a changed environment. Our results highlight the positive role that robustness and epistasis can have in adaptive evolution.
隐性变异是由表型对突变的稳健性引起的。在给定的遗传或环境背景下，隐性变异对表型没有影响，但在突变或环境变化后可能会产生影响。由于自然选择的进化适应需要表型变异，因此表型上显现的隐性遗传变异可能有助于进化适应。如果隐性变异碰巧适应于新环境，即“适应进化”，并且一旦被揭示出来就具有优势，那么这种情况是可能的。然而，隐性变异的这种促进作用尚未得到证实，部分原因是大多数相关工作都集中在整个生物体的复杂表型上，而这些生物体的遗传基础尚未完全了解。在这里，我们表明，积累了隐性变异的 RNA 酶种群比没有隐性变异的种群更能快速适应新的底物。对我们在基因型空间中不断进化的 RNA 群体的详细分析表明，隐性变异允许一个群体探索新的基因型，这些基因型只有在新的环境中才具有适应性。我们的观察结果表明，隐性变异包含了预先适应变化环境的新基因型。我们的研究结果强调了稳健性和上位性在适应性进化中可能具有的积极作用。
