Self-fertilization inherently restricts gene flow by reducing the fraction of offspring that can be produced by inter-population matings. Therefore, mating system transitions from outcrossing to selfing could result in reproductive isolation between selfing and outcrossing lineages and provide a starting point for speciation. In newly diverged lineages, for example after a transition to selfing, further reproductive isolation can be caused by a variety of prezygotic and post-zygotic mechanisms that operate before, during and after pollination. In animals, prezygotic barriers tend to evolve faster than post-zygotic ones. This is not necessarily the case for plants, for which the relative importance of post-mating, post-fertilization and early-acting post-zygotic barriers has been investigated far less. To test whether post-pollination isolation exists between populations of North American Arabidopsis lyrata that differ in breeding (self-incompatible versus self-compatible) and mating system (outcrossing versus selfing), we compared patterns of seed set after crosses made within populations, between populations of the same mating system and between populations with different mating systems. We found no evidence for post-pollination isolation between plants from selfing populations (self-compatible, low outcrossing rates) and outcrossing populations (self-incompatible, high outcrossing rates) via either prezygotic or early-acting post-zygotic mechanisms. Together with the results of other studies indicating the absence of reproductive barriers acting before and during pollination, we conclude that the transition to selfing in this study system has not led to the formation of reproductive barriers between selfing and outcrossing populations of North American A. lyrata.

中文翻译：

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没有证据表明北美拟南芥通过自交进行早期物种形成。

通过减少种群间交配产生的后代比例，自体受精本质上限制了基因流动。因此，交配系统从异交到自交的过渡可能导致自交和异交谱系之间的生殖隔离，并为物种形成提供起点。在新分化的谱系中，例如在过渡到自交之后，进一步的生殖隔离可能是由在授粉之前、期间和之后运作的各种合子前和合子后机制引起的。在动物中，合子前的屏障往往比合子后的屏障进化得更快。对于植物而言，情况并非一定如此，对于这些植物，对交配后、受精后和早期作用的合子后屏障的相对重要性的研究要少得多。为了测试在育种（自交与自交）和交配系统（异交与自交）方面不同的北美拟南芥种群之间是否存在授粉后隔离，我们比较了种群内杂交后的种子集模式，之间同一交配系统的种群以及不同交配系统的种群之间。我们没有发现自交种群（自交亲和、低异交率）和异交种群（自交不亲和、高异交率）之间通过合子前或早期作用后合子机制进行授粉后隔离的证据。连同其他研究的结果表明，在授粉之前和授粉期间不存在生殖障碍，