Department of Animal Ecology, Evolutionary Biology Centre, Uppsala University, Uppsala, Sweden.
PLoS One. 2011 Jan 31;6(1):e14628. doi: 10.1371/journal.pone.0014628.
Theory has identified a variety of evolutionary processes that may lead to speciation. Our study includes selection experiments using different host plants and test key predictions concerning models of speciation based on host plant choice, such as the evolution of host use (preference and performance) and assortative mating. This study shows that after only ten generations of selection on different resources/hosts in allopatry, strains of the seed beetle Callosobruchus maculatus develop new resource preferences and show resource-dependent assortative mating when given the possibility to choose mates and resources during secondary contact. The resulting reduced gene flow between the different strains remained for two generations after contact before being overrun by disassortative mating. We show that reduced gene flow can evolve in a population due to a link between host preference and assortative mating, although this result was not found in all lines. However, consistent with models of speciation, assortative mating alone is not sufficient to maintain reproductive isolation when individuals disperse freely between hosts. We conclude that the evolution of reproductive isolation in this system cannot proceed without selection against hybrids. Other possible factors facilitating the evolution of isolation would be longer periods of allopatry, the build up of local adaptation or reduced migration upon secondary contact.
理论已经确定了多种可能导致物种形成的进化过程。我们的研究包括使用不同宿主植物的选择实验，并测试了基于宿主植物选择的物种形成模型的关键预测，例如宿主使用的进化（偏好和表现）和交配的同型选择。这项研究表明，在异地选择不同资源/宿主的仅十代之后，斑豆象 Callosobruchus maculatus 的菌株在二次接触期间有机会选择配偶和资源时，会发展出新的资源偏好，并表现出资源依赖的同型交配。在接触后，不同菌株之间的基因流减少持续了两代，然后被异型交配所取代。我们表明，由于宿主偏好和同型交配之间的联系，基因流的减少可以在种群中进化，尽管并非所有品系都有此结果。然而，与物种形成模型一致，当个体在宿主之间自由分散时，同型交配本身不足以维持生殖隔离。我们得出结论，在没有对杂种选择的情况下，这个系统中的生殖隔离的进化是不可能的。促进隔离进化的其他可能因素包括更长的异地隔离期、局部适应性的增强或二次接触时迁移的减少。
