Department of Plant Biology and Ecology, Faculty of Biology, University of Seville, Apdo. 1095, 41080, Seville, Spain.
Phenology Lab, Department of Biodiversity, Biosciences Institute, UNESP - São Paulo State University, São Paulo, Brazil.
New Phytol. 2023 Apr;238(2):874-887. doi: 10.1111/nph.18767. Epub 2023 Feb 17.
Genetic divergence between species depends on reproductive isolation (RI) due to traits that reduce interspecific mating (prezygotic isolation) or are due to reduced hybrid fitness (postzygotic isolation). Previous research found that prezygotic barriers tend to be stronger than postzygotic barriers, but most studies are based on the evaluation of F hybrid fitness in early life cycle stages. We combined field and experimental data to determine the strength of 17 prezygotic and postzygotic reproductive barriers between two Lysimachia species that often co-occur and share pollinators. We assessed postzygotic barriers up to F hybrids and backcrosses. The two species showed near complete RI due to the cumulative effect of multiple barriers, with an uneven and asymmetric contribution to isolation. In allopatry, prezygotic barriers contributed more to reduce gene flow than postzygotic barriers, but their contributions were more similar in sympatry. The strength of postzygotic RI was up to three times lower for F progeny than for F or backcrossed progenies, and RI was only complete when late F stages and either F or backcrosses were accounted for. Our results thus suggest that the relative strength of postzygotic RI may be underestimated when its effects on late stages of the life cycle are disregarded.
物种间的遗传分化取决于生殖隔离（RI），这是由于减少种间交配的特征（前合子隔离）或由于杂种适应性降低（后合子隔离）所致。先前的研究发现，前合子障碍往往比后合子障碍更强，但大多数研究都是基于对早期生命周期阶段 F 杂种适应性的评估。我们结合了野外和实验数据，以确定两种经常共存且共享传粉者的报春花属物种之间的 17 种前合子和后合子生殖隔离的强度。我们评估了 F 杂种和回交的后合子障碍。由于多种障碍的累积效应，这两个物种表现出近完全的 RI，其隔离具有不均匀和不对称的贡献。在异地，前合子障碍比后合子障碍更有助于减少基因流动，但在同域时，它们的贡献更为相似。对于 F 后代而言，后合子 RI 的强度比 F 代或回交后代低三倍，只有当考虑到晚期 F 阶段和 F 代或回交时，RI 才是完整的。因此，我们的研究结果表明，如果忽略对生命周期晚期的影响，则可能低估后合子 RI 的相对强度。
