Olito Colin, Abbott Jessica K
Department of Biology, Division of Biodiversity and Evolution, Lund University, Lund, Sweden.
Evolution. 2025 May 6. doi: 10.1093/evolut/qpaf045.
The idea that sex-differences in selection drive the evolution of suppressed recombination between sex chromosomes is well-developed in population genetics. Yet, despite a now classic body of theory, empirical evidence that sexually antagonistic (SA) selection drives the evolution of recombination arrest remains equivocal and alternative hypotheses underdeveloped. Here, we investigate whether the length of "evolutionary strata" formed by chromosomal inversions (or other large-effect recombination modifiers) expanding the nonrecombining sex-linked region (SLR) on sex chromosomes can be informative of how selection influenced their fixation. We develop population genetic models to show how the length of an SLR-expanding inversion and the presence of partially recessive deleterious mutational variation affect the fixation probability of three different classes of inversions: (i) intrinsically neutral, (ii) directly beneficial (i.e., due to breakpoint or positional effects), and (iii) those capturing SA loci. Our models indicate that inversions capturing an SA locus initially in linkage disequilibrium with the ancestral SLR exhibit a strong fixation bias toward small inversions, while neutral, beneficial, and inversions capturing a genetically unlinked SA locus tend to favor larger inversions and exhibit similar distributions of fixed inversion lengths. The footprint of evolutionary stratum size left behind by different selection regimes is strongly influenced by parameters affecting the deleterious mutation load, the physical position of the ancestral SLR, and the distribution of new inversion lengths.
在群体遗传学中，关于选择中的性别差异驱动性染色体间重组抑制的进化这一观点已得到充分发展。然而，尽管有了现在经典的理论体系，但性拮抗（SA）选择驱动重组停滞进化的经验证据仍然模棱两可，其他假设也未得到充分发展。在这里，我们研究由染色体倒位（或其他大效应重组修饰因子）形成的“进化层”的长度，这些倒位扩展了性染色体上的非重组性连锁区域（SLR），是否能为选择如何影响它们的固定提供信息。我们开发了群体遗传模型，以展示扩展SLR的倒位长度以及部分隐性有害突变变异的存在如何影响三类不同倒位的固定概率：（i）本质上中性的，（ii）直接有益的（即由于断点或位置效应），以及（iii）那些捕获SA位点的倒位。我们的模型表明，最初与祖先SLR处于连锁不平衡状态捕获SA位点的倒位对小倒位表现出强烈的固定偏好，而中性、有益的倒位以及捕获遗传上不连锁SA位点的倒位倾向于更大的倒位，并表现出相似的固定倒位长度分布。不同选择机制留下的进化层大小印记受到影响有害突变负荷、祖先SLR的物理位置以及新倒位长度分布的参数的强烈影响。
