Emergent neutrality in adaptive asexual evolution.
Emergent neutrality in adaptive asexual evolution.
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DOI：
10.1534/genetics.111.132027
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发表时间：
2011-12
期刊：
影响因子：
3.3
通讯作者：
Lässig M
中科院分区：
文献类型：
--
作者：
Schiffels S;Szöllosi GJ;Mustonen V;Lässig M
在非重组基因组中，遗传连锁可能是一种重要的进化力量。连锁产生干扰相互作用，同时发生的突变影响彼此固定的机会。在这里，我们建立了一个综合的连锁基因组适应性进化模型，该模型将多个有益和有害突变之间的干扰相互作用整合到一个统一的框架中。通过近似解析解，我们预测了这些突变的固定率，以及在固定基因组位点上有益和有害等位基因的概率。我们发现，干扰相互作用产生了一种突发性中性机制：所有选择系数小于特征阈值的基因组位点都具有几乎随机的固定等位基因，并且这些位点上的有益和有害突变都具有接近中性的固定率。我们表明，这种动态不仅限制了适应的速度，而且限制了种群对当前环境的适应程度。我们将该模型应用于不同的场景：在依赖于时间的环境中的平稳适应和在固定环境中的平衡方法。在这两种情况下，分析预测与数值模拟很好地吻合。我们的研究结果表明，干扰会严重损害适应种群的生物功能，从而限制了连锁下的适应进化。
In nonrecombining genomes, genetic linkage can be an important evolutionary force. Linkage generates interference interactions, by which simultaneously occurring mutations affect each other’s chance of fixation. Here, we develop a comprehensive model of adaptive evolution in linked genomes, which integrates interference interactions between multiple beneficial and deleterious mutations into a unified framework. By an approximate analytical solution, we predict the fixation rates of these mutations, as well as the probabilities of beneficial and deleterious alleles at fixed genomic sites. We find that interference interactions generate a regime of emergent neutrality: all genomic sites with selection coefficients smaller in magnitude than a characteristic threshold have nearly random fixed alleles, and both beneficial and deleterious mutations at these sites have nearly neutral fixation rates. We show that this dynamic limits not only the speed of adaptation, but also a population’s degree of adaptation in its current environment. We apply the model to different scenarios: stationary adaptation in a time-dependent environment and approach to equilibrium in a fixed environment. In both cases, the analytical predictions are in good agreement with numerical simulations. Our results suggest that interference can severely compromise biological functions in an adapting population, which sets viability limits on adaptive evolution under linkage.