Hybridization dynamics between co‐occurring species in environments where human‐mediated changes take place are important to quantify for furthering our understanding of human impacts on species evolution and for informing management. The allis shad Alosa alosa (Linnaeus, 1758) and twaite shad Alosa fallax (Lacépède, 1803), two clupeids sister species, have been severely impacted by human activities across Europe. The shrinkage of A. alosa distribution range along with the decline of the remaining populations' abundance threatens its persistence. The main objective was to evaluate the extent of hybridization and introgression between those interacting species. We developed a set of 77 species‐specific SNP loci that allowed a better resolution than morphological traits as they enabled the detection of hybrids up to the third generation. Variable rates of contemporary hybridization and introgression patterns were detected in 12 studied sites across the French Atlantic coast. Mitochondrial markers revealed a cyto‐nuclear discordance almost invariably involving A. alosa individuals with an A. fallax mitochondrial DNA and provided evidence of historical asymmetric introgression. Overall, contemporary and historical introgression revealed by nuclear and mitochondrial markers strongly suggests that a transfer of genes occurs from A. fallax toward A. alosa genome since at least four generations. Moreover, the outcomes of introgression greatly depend on the catchments where local processes are thought to occur. Undoubtedly, interspecific interaction and gene flow should not be overlooked when considering the management of those species.

中文翻译：

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下降的Alosa alosa和Alosa fallax杂交的可变结果

在人类介导的变化发生的环境中，同时出现的物种之间的杂交动力学对于量化我们进一步了解人类对物种进化的影响以及为管理提供信息非常重要。在西鲱鲱鲱（林奈，1758）和twaite鲱鲱蝗（Lacépède，1803），两个姐姐clupeids品种，已通过欧洲人类活动的严重影响。芦荟的萎缩分布范围以及剩余人口数量的减少威胁到其持久性。主要目的是评估这些相互作用物种之间的杂交和渗入程度。我们开发了一组77种特定于物种的SNP位点，这些位点比形态性状具有更好的分辨率，因为它们能够检测到第三代杂交体。在法国大西洋沿岸的12个研究地点发现了当代杂交和渗入模式的变化率。线粒体标记揭示了细胞学核不一致几乎无一例外地涉及A.鲱个人与A.蝗线粒体DNA，并提供了历史不对称渗入的证据。总体而言，核和线粒体标记揭示的当代和历史基因渗入强烈表明，至少从四代开始，基因就从fallax移向了alosa基因组。而且，渗入的结果在很大程度上取决于认为发生局部过程的集水区。毫无疑问，在考虑管理这些物种时，种间相互作用和基因流不容忽视。