Ollivier Louis, Charlesworth Brian, Pouyet Fanny
Université Paris-Saclay, CNRS, Laboratoire Interdisciplinaire des Sciences du Numérique, Gif-sur-Yvette, France.
Institute of Ecology and Evolution, School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom.
PLoS Genet. 2025 Aug 4;21(8):e1011798. doi: 10.1371/journal.pgen.1011798. eCollection 2025 Aug.
An important aim of population genetics is to elucidate the processes affecting genetic diversity across regions of the genome and across species. Canonical population genetic models of sexually reproducing species define the rate of meiotic recombination in terms of the frequency of recombination events per site per sexual generation. This paper studies the interplay of several factors with respect to their effects on neutral genetic diversity in a facultatively sexual, diploid, unicellular species such as yeast. The relevant factors are the prevalence of meiosis versus mitosis, the recombination rate, and the selection and dominance coefficients at loci under positive selection. We assume that many generations of mitotic cell divisions are interspersed with episodes of sexual reproduction, in which all individuals in the population undergo meiosis, followed by random matings among the resulting gametes. Our findings reveal that a single hard selective sweep can reduce neutral nucleotide site diversity across the entire genome, provided that the frequency of meiotic events is sufficiently low, and that the effects of a selective sweep on levels of neutral diversity at sites linked to the target of selection can be markedly different from those predicted by standard models of sweeps based on obligate sexuality. Species that reproduce by facultative sex are thus likely to exhibit unusual patterns of genetic diversity.
群体遗传学的一个重要目标是阐明影响基因组各区域以及不同物种间遗传多样性的过程。有性生殖物种的经典群体遗传模型根据每个有性世代每个位点的重组事件频率来定义减数分裂重组率。本文研究了几个因素在兼性有性、二倍体单细胞物种（如酵母）中对中性遗传多样性的影响之间的相互作用。相关因素包括减数分裂与有丝分裂的发生率、重组率以及正选择位点的选择系数和显性系数。我们假设多代有丝分裂细胞分裂穿插着有性生殖事件，在此期间群体中的所有个体都进行减数分裂，随后产生的配子之间随机交配。我们的研究结果表明，只要减数分裂事件的频率足够低，一次强烈的选择性清除就能降低整个基因组的中性核苷酸位点多样性，而且选择性清除对与选择目标相关位点的中性多样性水平的影响可能与基于专性有性生殖的标准清除模型所预测的显著不同。因此，通过兼性有性生殖繁殖的物种可能会表现出不寻常的遗传多样性模式。
