Secondary contact may have important implications for ecological and evolutionary processes; however, few studies have tracked the outcomes of secondary contact from its onset in natural ecosystems. We evaluated an anadromous alewife (Alosa pseudoharengus) reintroduction project in Rogers Lake (Connecticut, USA), which contains a landlocked alewife population that was isolated as a result of colonial‐era damming. After access to the ocean was restored, adult anadromous alewife were stocked into the lake. We assessed anadromous juvenile production, the magnitude and direction of introgression, and the potential for competition between ecotypes. We obtained fin clips from all adult alewife stocked into the lake during the restoration and a sample of juveniles produced in the lake two years after the stocking began. We assessed the ancestry of juveniles using categorical assignment and pedigree reconstruction with newly developed microhaplotype genetic markers. Anadromous alewives successfully spawned in the lake and hybridized with the landlocked population. Parentage assignments revealed that male and female anadromous fish contributed equally to juvenile F1 hybrids. The presence of landlocked backcrosses shows that some hybrids were produced within the first two years of secondary contact, matured in the lake, and reproduced. Therefore, introgression appears directional, from anadromous into landlocked, in the lake environment. Differences in estimated abundance of juveniles of different ecotypes in different habitats were also detected, which may reduce competition between ecotypes as the restoration continues. Our results illustrate the utility of restoration projects to study the outcomes of secondary contact in real ecosystems.

中文翻译：

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恢复介导的二次接触导致被殖民时代大坝隔开的alewife生态型渗入

次生接触可能对生态和进化过程产生重要影响；然而，很少有研究追踪自然生态系统中二次接触的结果。我们评估了一个不佳的alewife（Alosa pseudoharengus ）罗杰斯湖（美国康涅狄格州）的重新引入项目，其中包含一个内陆的ewewife种群，由于殖民时期的筑坝而被隔离。恢复出海通道后，成年的无翅金线鱼被放养到湖中。我们评估了青少年的无节制生产，渗入的程度和方向以及生态型之间竞争的可能性。在恢复期间，我们从放养到湖中的所有成年白ew中获取了鳍片，并在放养两年后在湖中生产了幼体样本。我们使用分类分配和带有新开发的微单倍型遗传标记的血统重建评估了青少年的血统。凤尾鱼在湖中成功产卵，并与内陆人口杂交。亲子关系的研究表明，雄性和雌性无性鱼对幼年F1杂种的贡献相同。内陆回交的存在表明，一些杂种在次生接触的头两年内产生，在湖中成熟并繁殖。因此，在湖泊环境中，渗入表现为定向的，从适生到内陆。还发现了不同生境中不同生态类型的未成年人的估计丰度差异，这可能会随着恢复的继续而减少生态类型之间的竞争。我们的结果说明了恢复项目在研究真实生态系统中二次接触的结果中的作用。内陆回交的存在表明，一些杂种在次生接触的头两年内产生，在湖中成熟并繁殖。因此，在湖泊环境中，渗入表现为定向的，从适生到内陆。还发现了不同生境中不同生态类型的未成年人的估计丰度差异，这可能会随着恢复的继续而减少生态类型之间的竞争。我们的结果说明了恢复项目在研究真实生态系统中二次接触的结果中的作用。内陆回交的存在表明，一些杂种在次生接触的头两年内产生，在湖中成熟并繁殖。因此，在湖泊环境中，渗入表现为定向的，从适生到内陆。还发现了不同生境中不同生态类型的未成年人的估计丰度差异，这可能会随着恢复的继续而减少生态类型之间的竞争。我们的结果说明了恢复项目在研究真实生态系统中二次接触的结果中的作用。随着恢复的进行，这可能会减少生态型之间的竞争。我们的结果说明了恢复项目在研究真实生态系统中二次接触的结果中的作用。随着恢复的进行，这可能会减少生态型之间的竞争。我们的结果说明了恢复项目在研究真实生态系统中二次接触的结果中的作用。