High estimates of inbreeding depression have been obtained in many plant populations with high selfing rates. However, deleterious mutations might be purged from such populations as a result of selfing. I developed a simulation model assuming the presence of mutations at two sets of loci, namely, early- and late-acting loci, and the selective abortion of embryos coupled with ovule overproduction. In the model, early-acting loci are expressed during embryo initiation, and less vigorous embryos are aborted. Late-acting loci are expressed after selective abortion ends; the surviving embryos (seeds) compete, and some of them form the next generation. If mutations are allowed to occur in both early- and late-acting loci, both types increase in frequency in populations with high selfing rates. However, this phenomenon does not occur if mutations occur only in the early- or only in the late-acting loci. Consistent results are observed even if the total number of loci in which mutations are allowed to occur is the same for simulations with both early- and late-acting loci, only early-acting loci, or only late-acting loci, indicating that the presence of both types of loci is the causal factor. Thus, the two-stage effect, or occurrence of both early- and late-acting mutations, promotes the maintenance of these mutations in populations with high selfing rates.

在许多自交率很高的植物种群中，对近交抑制的估计很高。但是，由于自交，有害突变可能会从这些种群中清除。我开发了一个模拟模型，假设在两个基因座（即早期和晚期作用基因座）处存在突变，以及胚胎的选择性流产和胚珠过度生产。在该模型中，早期作用的基因座在胚胎萌发过程中表达，而活力较弱的胚胎则被流产。选择性流产结束后表达晚期作用基因座。存活的胚胎（种子）竞争，其中一些形成了下一代。如果允许在早期和晚期作用基因座中发生突变，则在高自交率人群中两种类型的频率都会增加。然而，如果仅在早期或晚期作用基因座中发生突变，则不会发生此现象。即使对于早期和晚期作用基因座，仅早期作用基因座或仅晚期作用基因座的模拟，即使允许发生突变的基因座总数相同，也观察到一致的结果。两种类型基因座中的一个是因果因素。因此，两阶段效应或早期和晚期作用突变的发生，促进了高自交率人群中这些突变的维持。表示这两种基因座的存在都是因果关系。因此，两阶段效应或早期和晚期作用突变的发生，促进了高自交率人群中这些突变的维持。表示这两种基因座的存在都是因果关系。因此，两阶段效应或早期和晚期作用突变的发生，促进了高自交率人群中这些突变的维持。