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普适性解释来阐明有性繁殖种群抵御无性类群入侵的内在机制，但已有研究证实，在结构种群中，有性繁殖个体可在竞争中胜过无性繁殖个体。然而，当前学界仍未明确，在自然界普遍存在的弱结构种群中，携带适应代价的有性繁殖能否得以维持。本研究针对存在反复突变的结构种群，探究专性有性繁殖类群抵御无性类群入侵的临界条件。我们以所有亚种群（deme）对间的平均种群分化系数（Fixation Index, Fst）作为量化指标，确定了能够使无性类群处于竞争劣势所需的种群结构水平。研究表明，维持有性繁殖所需的临界Fst值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中等水平。当种群同时存在有利突变与有害突变、突变率足够高，且有害突变具有中等选择强度（此时穆勒棘轮（Muller's Ratchet）的效应达到最大化）时，维持有性繁殖所需的Fst值会更低。此外，当亚种群总数较多时，维持有性繁殖所需的临界Fst值也会降低。当亚种群间的两两距离差异显著（例如沿一维线性阵列分布）时，维持有性繁殖所需的Fst值会更低，但这一效应通常较为微弱，尤其当存在一定比例的长距离扩散时更是如此。