The rate at which asexual populations cross fitness valleys.
The rate at which asexual populations cross fitness valleys.
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DOI：
10.1016/j.tpb.2009.02.006
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发表时间：
2009-06
影响因子：
1.4
通讯作者：
Feldman, Marcus W.
中科院分区：
文献类型：
--
作者：
Weissman, Daniel B.;Desai, Michael M.;Fisher, Daniel S.;Feldman, Marcus W.
复杂的性状往往涉及不同遗传位点之间的相互作用。这可能会导致符号上位性，即一组突变单独是有害的或中性的，但组合起来会带来适应性益处。为了获得有益的基因型，无性种群必须首先获得有害或中性的中间体，从而穿过适合度谷或适合度坪。在这里，我们提出了一个完整的，直观的理论描述跨越整个频谱的可能的参数制度的山谷穿越过程。我们计算种群穿越任意宽度的适应谷或高原的速率，作为突变率，种群大小和中间体适应度的函数。我们发现，当中间体接近中性，一个大的人口可以跨越甚至广泛的健身谷非常快，所以跨谷动态可能是常见的，即使突变，直接增加健身也是可能的。因此，大种群的进化动力学可能对适应度景观的扩展区域的结构很敏感-种群可能会放弃直接上坡的路径，而选择穿越山谷和高原的路径，最终导致更适合的基因型。在较小的人群中，我们发现，低于阈值大小，这取决于宽度的健身谷和强度的选择对中间基因型，山谷杂交是不太可能的，因此进化动力学的影响较小，由遥远的地区的健身景观。
Complex traits often involve interactions between different genetic loci. This can lead to sign epistasis, whereby a set of mutations are individually deleterious or neutral but in combination confer a fitness benefit. In order to acquire the beneficial genotype, an asexual population must cross a fitness valley or plateau by first acquiring the deleterious or neutral intermediates. Here, we present a complete, intuitive theoretical description of the valley-crossing process across the full spectrum of possible parameter regimes. We calculate the rate at which a population crosses a fitness valley or plateau of arbitrary width, as a function of the mutation rates, the population size, and the fitnesses of the intermediates. We find that when intermediates are close to neutral, a large population can cross even wide fitness valleys remarkably quickly, so that valley-crossing dynamics may be common even when mutations that directly increase fitness are also possible. Thus the evolutionary dynamics of large populations can be sensitive to the structure of an extended region of the fitness landscape – the population may be likely to pass up directly uphill paths in favor of paths across valleys and plateaus that lead eventually to fitter genotypes. In smaller populations, we find that below a threshold size which depends on the width of the fitness valley and the strength of selection against intermediate genotypes, valley-crossing is much less likely and hence the evolutionary dynamics are less influenced by distant regions of the fitness landscape.
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