It is commonly observed that plant species' range margins are enriched for increased selfing rates and, in otherwise self‐incompatible species, for self‐compatibility (SC). This has often been attributed to a response to selection under mate and/or pollinator limitation. However, range expansion can also cause reduced inbreeding depression, and this could facilitate the evolution of selfing in the absence of mate or pollinator limitation. Here, we explore this idea using spatially explicit individual‐based simulations of a range expansion, in which inbreeding depression, variation in self‐incompatibility (SI), and mate availability evolve. Under a wide range of conditions, the simulated range expansion brought about the evolution of selfing after the loss of SI in range‐marginal populations. Under conditions of high recombination between the self‐incompatibility locus (S‐locus) and viability loci, SC remained marginal in the expanded metapopulation and could not invade the range core, which remained self‐incompatible. In contrast, under low recombination and migration rates, SC was frequently able to displace SI in the range core by maintaining its association with a genomic background with purged genetic load. We conclude that the evolution of inbreeding depression during a range expansion promotes the evolution of SC at range margins, especially under high rates of recombination.‬

中文翻译：

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范围扩展中自不相容性的丧失

通常观察到，植物物种的范围边缘因自交率增加而增加，并且在其他自交不相容的物种中，自交亲和性（SC）。这通常归因于对配偶和/或传粉者限制下的选择的反应。然而，范围扩大也可以减少近交抑制，这可以促进在没有配偶或传粉者限制的情况下自交的进化。在这里，我们使用空间明确的基于个体的范围扩展模拟来探索这个想法，其中近交衰退、自交不亲和性 (SI) 的变化和配偶可用性不断发展。在广泛的条件下，模拟的范围扩展带来了范围边缘种群SI损失后的自交进化。在自交不亲和基因座（S-基因座）和生存力基因座之间高度重组的条件下，SC在扩大的复合种群中仍然处于边缘，不能侵入范围核心，保持自交不亲和。相比之下，在低重组和迁移率下，SC 通过保持其与具有清除遗传负载的基因组背景的关联，经常能够取代范围核心中的 SI。我们得出的结论是，在范围扩张期间近交衰退的演变促进了范围边缘 SC 的演变，尤其是在高重组率的情况下。SC 通过保持其与具有清除遗传负载的基因组背景的关联，经常能够取代范围核心中的 SI。我们得出的结论是，在范围扩张期间近交衰退的演变促进了范围边缘 SC 的演变，尤其是在高重组率的情况下。SC 通过保持其与具有清除遗传负载的基因组背景的关联，经常能够取代范围核心中的 SI。我们得出的结论是，在范围扩展期间近交衰退的演变促进了范围边缘 SC 的演变，尤其是在高重组率的情况下。