Forschungsinstitut für biologischen Landbau (FiBL), Department of crop Sciences, Ackerstrasse 113, CH-5070, Frick, Switzerland.
Department of Environmental Sciences, Section Conservation Biology (NLU), University of Basel, St. Johanns-Vorstadt 10, CH-4056, Basel, Switzerland.
Evolution. 2018 Sep;72(9):1851-1862. doi: 10.1111/evo.13556. Epub 2018 Jul 27.
Quantifying the relative contribution of multiple isolation barriers to gene flow between recently diverged species is essential for understanding speciation processes. In parapatric populations, local adaptation is thought to be a major contributor to the evolution of reproductive isolation. However, extrinsic postzygotic barriers assessed in reciprocal transplant experiments are often neglected in empirical assessments of multiple isolation barriers. We analyzed multiple isolation barriers between two closely related species of the plant genus Dianthus, a genus characterized by the most rapid species diversification in plants reported so far. Although D. carthusianorum L. and D. sylvestris Wulf. can easily be hybridized in crossing experiments, natural hybrids are rare. We found that in parapatry, pollinator-mediated prezygotic reproductive isolation barriers are important for both D. carthusianorum (0.761) and D. sylvestris (0.468). In contrast to D. carthusianorum, high hybrid viability in D. sylvestris (-0.491) was counteracted by strong extrinsic postzygotic isolation (0.900). Our study highlights the importance of including reciprocal transplant experiments for documenting extrinsic postzygotic isolation and demonstrates clearly divergent strategies and hence asymmetric pre- and postzygotic reproductive isolation between closely related species. It also suggests that pollinator-mediated and ecological isolation could have interacted in synergistic ways, further stimulating rapid speciation in Dianthus.
量化多个隔离障碍对新近分化物种基因流动的相对贡献对于理解物种形成过程至关重要。在邻域种群中，局部适应被认为是生殖隔离进化的主要因素。然而，在对多个隔离障碍进行经验评估时，往往会忽略在正反移植实验中评估的外在合子后隔离障碍。我们分析了植物属丁香的两个密切相关物种之间的多个隔离障碍，该属是迄今为止植物物种多样化最快的属。尽管 D. carthusianorum L. 和 D. sylvestris Wulf. 可以在杂交实验中轻松杂交，但自然杂种却很少见。我们发现，在邻域中，传粉媒介介导的合子前生殖隔离障碍对 D. carthusianorum（0.761）和 D. sylvestris（0.468）都很重要。与 D. carthusianorum 相反，D. sylvestris 中的高杂交活力（-0.491）被强烈的外在合子后隔离（0.900）所抵消。我们的研究强调了包括正反移植实验来记录外在合子后隔离的重要性，并清楚地表明了密切相关物种之间存在明显不同的策略，从而导致了不对称的合子前和合子后生殖隔离。它还表明，传粉媒介介导的和生态隔离可能以协同方式相互作用，进一步刺激了丁香属的快速物种形成。
