Department of Biology, York University, 4700 Keele St. Toronto, Ontario M3J 1P3, Canada.
Evolution. 2010 Dec;64(12):3495-510. doi: 10.1111/j.1558-5646.2010.01094.x.
Theoretical and empirical comparisons of molecular diversity in selfing and outcrossing plants have primarily focused on long-term consequences of differences in mating system (between species). However, improving our understanding of the causes of mating system evolution requires ecological and genetic studies of the early stages of mating system transition. Here, we examine nuclear and chloroplast DNA sequences and microsatellite variation in a large sample of populations of Arabidopsis lyrata from the Great Lakes region of Eastern North American that show intra- and interpopulation variation in the degree of self-incompatibility and realized outcrossing rates. Populations show strong geographic clustering irrespective of mating system, suggesting that selfing either evolved multiple times or has spread to multiple genetic backgrounds. Diversity is reduced in selfing populations, but not to the extent of the severe loss of variation expected if selfing evolved due to selection for reproductive assurance in connection with strong founder events. The spread of self-compatibility in this region may have been favored as colonization bottlenecks following glaciation or migration from Europe reduced standing levels of inbreeding depression. However, our results do not suggest a single transition to selfing in this system, as has been suggested for some other species in the Brassicaceae.
自交和异交植物的分子多样性的理论和实证比较主要集中在交配系统（种间）差异的长期后果上。然而，要提高我们对交配系统进化原因的理解，就需要对交配系统过渡的早期阶段进行生态和遗传研究。在这里，我们研究了来自北美东部大湖地区的大量拟南芥 lyrata 种群的核和叶绿体 DNA 序列和微卫星变异，这些种群在自交不亲和程度和实现异交率方面表现出种内和种间的变异。种群表现出强烈的地理聚类，无论交配系统如何，这表明自交要么多次进化，要么已经传播到多个遗传背景。自交种群的多样性减少，但并没有减少到如果自交是由于与强烈的奠基事件相关的生殖保证选择而进化所预期的严重变异损失程度。在这个地区，自交亲和性的传播可能是有利的，因为冰川作用或从欧洲的迁徙导致的殖民瓶颈降低了近交衰退的水平。然而，我们的结果并不表明在这个系统中存在单一的自交转变，就像在一些其他芸苔科物种中所表明的那样。
