Am Nat. 2023 May;201(5):694-711. doi: 10.1086/723454. Epub 2023 Apr 4.
AbstractSimple polyembryony, where one gametophyte produces multiple embryos with different sires but the same maternal haplotype, is common among vascular plants. We develop an infinite-sites, forward population genetics model showing that together polyembryony's two benefits-"reproductive compensation" achieved by providing a backup for inviable embryos and the opportunity to favor the fitter of surviving embryos-can favor its evolution. Our model tests how these factors can favor the evolution of polyembryony and how these underlying benefits of polyembryony shape the genetic load under a range of biological parameters. While these two benefits are difficult to disentangle in nature, we construct variant models of polyembryony that either only include or only exclude the opportunity for reproductive compensation. We find that reproductive compensation strongly favors the evolution of polyembryony and that polyembryony is favored much more weekly in its absence, suggesting that the benefit of a backup embryo is the major force favoring polyembryony. Remarkably, we find nearly identical results in cases in which mutations impact either embryonic or postembryonic fitness (no pleiotropy) and in cases in which mutations have identical effects on embryonic and postembryonic fitness (extreme pleiotropy). Finally, we find that the consequences of polyembryony depend on its function-polyembryony results in a decrease in mean embryonic fitness when acting as a mechanism of embryo compensation and ultimately increases mean embryonic fitness when we exclude this potential benefit.
简单多胚现象，即一个配子体产生多个具有不同父系但相同母系单倍型的胚胎，在维管植物中很常见。我们开发了一个无限位点的正向群体遗传学模型，表明多胚现象的两个好处——通过为不可育胚胎提供备份来实现生殖补偿，以及有机会选择存活胚胎中更健康的胚胎——可以促进其进化。我们的模型检验了这些因素如何促进多胚现象的进化，以及多胚现象的这些潜在好处如何在一系列生物学参数下塑造遗传负荷。虽然这两个好处在自然界中很难区分，但我们构建了多胚现象的变体模型，这些模型要么只包括生殖补偿的机会，要么只排除生殖补偿的机会。我们发现生殖补偿强烈促进了多胚现象的进化，如果没有生殖补偿，多胚现象的进化就会弱得多，这表明备份胚胎的好处是促进多胚现象进化的主要力量。值得注意的是，我们在突变影响胚胎或胚胎后适应度（无多效性）的情况下，以及在突变对胚胎和胚胎后适应度具有相同影响（极端多效性）的情况下，都得到了几乎相同的结果。最后，我们发现多胚现象的后果取决于其功能——当多胚现象作为胚胎补偿的一种机制时，它会降低平均胚胎适应度，而当我们排除这种潜在好处时，它最终会增加平均胚胎适应度。
