Hybridization between invasive and native species has raised global concern, given the dramatic increase in species range shifts and pest outbreaks due to anthropogenic dispersal. Nevertheless, secondary contact between sister lineages of local and invasive species provides a natural laboratory to understand the factors that determine introgression and the maintenance or loss of species barriers. Here, we characterize the early evolutionary outcomes following secondary contact between invasive Helicoverpa armigera and native H. zea in Brazil. We carried out whole-genome resequencing of Helicoverpa moths from Brazil in two temporal samples: during the outbreak of H. armigera in 2013, and 2017. There is evidence for a burst of hybridization and widespread introgression from local H. zea into invasive H. armigera coinciding with H. armigera expansion in 2013. However, in H. armigera, the admixture proportion and the length of introgressed blocks were significantly reduced between 2013 and 2017, suggesting selection against admixture. In contrast to the genome-wide pattern, there was striking evidence for adaptive introgression of a single region from the invasive H. armigera into local H. zea, including an insecticide-resistance allele that increased in frequency over time. In summary, despite extensive gene-flow after secondary contact, the species boundaries are largely maintained except for the single introgressed region containing the insecticide-resistant locus. We document the worst-case scenario for an invasive species, in which there are now two pest species instead of one, and the native species has acquired resistance to pyrethroid insecticides through introgression.

中文翻译：

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本地玉米夜蛾和入侵棉铃虫之间跨半透性物种边界的适应性渗入。

鉴于人为扩散导致物种范围变化和害虫爆发急剧增加，入侵物种与本地物种之间的杂交已引起全球关注。然而，当地物种和入侵物种的姐妹谱系之间的二次接触提供了一个天然的实验室，以了解决定基因渗入以及物种屏障的维持或丧失的因素。在这里，我们描述了巴西入侵性棉铃虫和本地玉米棉铃虫二次接触后的早期进化结果。我们对来自巴西的棉铃虫蛾的两个时间样本进行了全基因组重测序：2013 年和 2017 年棉铃虫爆发期间。有证据表明当地棉铃虫爆发了杂交，并广泛渗入到了入侵的棉铃虫中。 2013年，棉铃虫的扩张与棉铃虫的扩张相一致。然而，在棉铃虫中，2013年至2017年期间，混合比例和渗入块的长度显着减少，表明对混合的选择。与全基因组模式相反，有惊人的证据表明，单个区域从入侵的棉铃虫到当地的玉米虫有适应性渗入，其中包括随着时间的推移频率增加的杀虫剂抗性等位基因。总之，尽管二次接触后存在广泛的基因流，但除了包含抗杀虫剂基因座的单个渗入区域外，物种边界在很大程度上得到维持。我们记录了入侵物种的最坏情况，其中现在有两种害虫物种而不是一种，并且本地物种通过基因渗入获得了对拟除虫菊酯杀虫剂的抗性。