Transient amplifiers of selection and reducers of fixation for death-Birth updating on graphs
Transient amplifiers of selection and reducers of fixation for death-Birth updating on graphs
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DOI：
10.1371/journal.pcbi.1007529
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发表时间：
2020-01-01
影响因子：
4.3
通讯作者：
Dementieva, Yulia A.
中科院分区：
文献类型：
--
作者：
Allen, Benjamin;Sample, Christine;Dementieva, Yulia A.
进化种群的空间结构影响着自然选择和遗传漂移之间的平衡。一些结构放大了选择，增加了适应度差异在决定哪些突变变得固定方面所起的作用。其他结构抑制了选择，减少了适应度差异的影响，增加了随机机会的作用。这种现象可以通过将空间结构表示为图来建模，其中个体占据顶点。根据指定的更新规则，出生和死亡是随机发生的。我们研究死亡-出生更新：一个人被选中死亡，然后它的邻居竞争繁殖到空位上。以前的数值实验表明，用于这一过程的选择放大器要么很少，要么根本不存在。对于弱选择机制，我们引入了一个微扰方法来解决这个问题，这意味着突变具有很小的适应度影响。我们证明了弱选择下的注视概率可以用随机游动的合并时间来计算。这一结果自然导致了对有效人口规模的新定义。使用这种方法和其他方法，我们发现了第一批已知的死产过程的瞬时选择放大器(放大特定范围的适应值的选择的曲线图)的例子。我们还展示了新的“固定减少器”家族，它们降低了所有突变的固定概率，无论是有益的还是有害的。作者摘要自然选择通常被认为是“适者生存”，但随机机会在突变持续存在和被消除的过程中发挥着重要作用。选择与随机性的平衡受到空间结构的影响--个体在其栖息地内的排列方式。一些结构放大了选择的效果，因此只有最合适的突变才可能持续存在。另一些基因则抑制了选择的效果，使得基因的存活主要是一个随机机会的问题。我们使用一个称为“死亡-出生过程”的数学模型来研究这个问题。此前的研究发现，空间结构很少(如果有的话)放大这一过程的选择。在这里，我们报告了空间结构确实可以放大选择，至少对于适应度影响较小的突变是如此。我们还确定了减少任何新突变传播的结构，无论是有益的还是有害的。我们的工作引入了新的数学技术来评估种群结构如何影响自然选择。
The spatial structure of an evolving population affects the balance of natural selection versus genetic drift. Some structures amplify selection, increasing the role that fitness differences play in determining which mutations become fixed. Other structures suppress selection, reducing the effect of fitness differences and increasing the role of random chance. This phenomenon can be modeled by representing spatial structure as a graph, with individuals occupying vertices. Births and deaths occur stochastically, according to a specified update rule. We study death-Birth updating: An individual is chosen to die and then its neighbors compete to reproduce into the vacant spot. Previous numerical experiments suggested that amplifiers of selection for this process are either rare or nonexistent. We introduce a perturbative method for this problem for weak selection regime, meaning that mutations have small fitness effects. We show that fixation probability under weak selection can be calculated in terms of the coalescence times of random walks. This result leads naturally to a new definition of effective population size. Using this and other methods, we uncover the first known examples of transient amplifiers of selection (graphs that amplify selection for a particular range of fitness values) for the death-Birth process. We also exhibit new families of "reducers of fixation", which decrease the fixation probability of all mutations, whether beneficial or deleterious.Author summary Natural selection is often thought of as "survival of the fittest", but random chance plays a significant role in which mutations persist and which are eliminated. The balance of selection versus randomness is affected by spatial structure-how individuals are arranged within their habitat. Some structures amplify the effects of selection, so that only the fittest mutations are likely to persist. Others suppress the effects of selection, making the survival of genes primarily a matter of random chance. We study this question using a mathematical model called the "death-Birth process". Previous studies have found that spatial structure rarely, if ever, amplifies selection for this process. Here we report that spatial structure can indeed amplify selection, at least for mutations with small fitness effects. We also identify structures that reduce the spread of any new mutation, whether beneficial or deleterious. Our work introduces new mathematical techniques for assessing how population structure affects natural selection.