Secondary contact in close relatives can result in hybridization and the admixture of previously isolated gene pools. However, after an initial period of hybridization, reproductive isolation can evolve through different processes and lead to the interruption of gene flow and the completion of the speciation process. Omocestus minutissimus and O . uhagonii are two closely related grasshoppers with partially overlapping distributions in the Central System mountains of the Iberian Peninsula. To analyse spatial patterns of historical and/or contemporary hybridization between these two taxa and understand how species boundaries are maintained in the region of secondary contact, we sampled sympatric and allopatric populations of the two species and obtained genome‐wide single nucleotide polymorphism data using a restriction site‐associated DNA sequencing approach. We used Bayesian clustering analyses to test the hypothesis of contemporary hybridization in sympatric populations and employed a suite of phylogenomic approaches and a coalescent‐based simulation framework to evaluate alternative hypothetical scenarios of interspecific gene flow. Our analyses rejected the hypothesis of contemporary hybridization but revealed past introgression in the area where the distributions of the two species overlap. Overall, these results point to a scenario of historical gene flow after secondary contact followed by the evolution of reproductive isolation that currently prevents hybridization among sympatric populations.

中文翻译：

---

一个古老事件的基因组足迹：单核苷酸多态性数据揭示了历史杂交以及随后在部分分布重叠的两个最近散布的蝗虫中生殖屏障的演变。

近亲的二次接触可导致杂交和先前分离的基因库的混合。但是，在杂交的初始阶段之后，生殖分离会通过不同的过程进行，并导致基因流的中断和物种形成过程的完成。Omocestus minutissimus和Ò。 乌哈贡尼是在伊比利亚半岛的中央系统山脉中分布紧密重叠的两只蚂蚱。为了分析这两个类群之间历史和/或当代杂交的空间模式并了解在次生接触区域中物种边界如何维持，我们对两个物种的同胞和异源种群进行了采样，并使用a获得了全基因组范围的单核苷酸多态性数据。限制性酶切位点相关的DNA测序方法。我们使用贝叶斯聚类分析来检验同胞种群中当代杂交的假设，并采用了一套系统生物学方法和基于聚结的模拟框架来评估种间基因流的其他假设情景。我们的分析拒绝了当代杂交的假设，但揭示了过去在两种物种分布重叠的区域中的基因渗入。总的来说，这些结果表明了二次接触后历史基因流动的场景，随后是生殖隔离的进化，目前阻止了同胞种群之间的杂交。