Data from: The maintenance of obligate sex in finite, structured populations subject to recurrent beneficial and deleterious mutation

Although there is no known general explanation as to why sexual populations resist asexual invasion, previous work has shown that sexuals can outcompete asexuals in structured populations. However, it is currently unknown whether costly sex can be maintained with the weak structure that is commonly observed in nature. We investigate the conditions under which obligate sexuals resist asexual invasion in structured populations subject to recurrent mutation. We determine the level of population structure needed to disfavour asexuals, as calculated using the average Fst between all pairs of demes. We show that the critical Fst needed to maintain sex decreases as the population size increases, and approaches modest levels as observed in many natural populations. Sex is maintained with lower Fst if there are both advantageous and deleterious mutation, if mutation rates are sufficiently high, and if deleterious mutants have intermediate selective strengths, which maximises the effect of Muller's Ratchet. Additionally, the critical Fst needed to maintain sex is lower when there are a large number of subpopulations. Lower Fst values are needed to maintain sex when demes vary substantially in their pairwise distances (e.g., when arrayed along one dimension), although this effect is often modest, especially if some long-distance dispersal is present.

尽管目前尚无公认的通用理论解释有性种群为何能够抵御无性生殖入侵，但已有研究证实，在结构化种群中，有性个体可在竞争中胜过无性个体。然而，当前尚不清楚，在自然界中普遍存在的弱结构化种群中，具备繁殖成本的有性生殖能否得以维持。本研究探究了存在复发性突变的结构化种群中，专性有性个体抵御无性生殖入侵的条件。我们通过所有亚群（deme）对间的平均Fst（种群分化固定指数）计算得出了不利于无性个体所需的种群结构化水平。研究表明，维持有性生殖所需的临界Fst会随种群规模扩大而降低，并趋近于许多自然种群中观测到的适中水平。当种群同时存在有利突变与有害突变、突变率足够高，且有害突变具备中等选择强度（此时穆勒棘轮（Muller's Ratchet）的效应达到最大化）时，维持有性生殖所需的Fst阈值更低。此外，当亚群数量较多时，维持有性生殖所需的临界Fst也会更低。当亚群间的成对距离差异显著时（例如沿一维线性排列的亚群），维持有性生殖所需的Fst阈值会更低，但该效应通常较为微弱，尤其当存在一定程度的长距离扩散时更是如此。