Fitness flux and ubiquity of adaptive evolution
Fitness flux and ubiquity of adaptive evolution
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DOI：
10.1073/pnas.0907953107
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发表时间：
2010-03-02
影响因子：
11.1
通讯作者：
Laessig, Michael
中科院分区：
文献类型：
--
作者：
Mustonen, Ville;Laessig, Michael
自然选择有利于群体中更适应的变体，但实际的进化过程可能会因突变和遗传漂变而降低适应度。自然选择如何塑造分子生物系统的随机进化？在这里，我们推导出一个关于种群适应度通量的定理，定义为其基因型频率变化的选择性效应。适应度通量定理将费希尔的自然选择基本定理推广到进化过程，包括突变、遗传漂变和时间依赖性选择。它表明种群的一般状态是适应性进化：由于有益的变化超过有害的变化而产生正的适应通量。特别是，平稳非平衡演化过程被预测具有适应性。在特定的非平稳条件下，特别是在人口规模减少期间，平均适应度通量可能变为负值。我们证明这些预测与细菌和噬菌体实验以及果蝇基因组数据一致。我们的分析将适应通量确立为分子进化适应的通用衡量标准。
Natural selection favors fitter variants in a population, but actual evolutionary processes may decrease fitness by mutations and genetic drift. How is the stochastic evolution of molecular biological systems shaped by natural selection? Here, we derive a theorem on the fitness flux in a population, defined as the selective effect of its genotype frequency changes. The fitness-flux theorem generalizes Fisher's fundamental theorem of natural selection to evolutionary processes including mutations, genetic drift, and time-dependent selection. It shows that a generic state of populations is adaptive evolution: there is a positive fitness flux resulting from a surplus of beneficial over deleterious changes. In particular, stationary nonequilibrium evolution processes are predicted to be adaptive. Under specific nonstationary conditions, notably during a decrease in population size, the average fitness flux can become negative. We show that these predictions are in accordance with experiments in bacteria and bacteriophages and with genomic data in Drosophila. Our analysis establishes fitness flux as a universal measure of adaptation in molecular evolution.