Reid Kerry, Carlos Garza John, Gephard Steven R, Caccone Adalgisa, Post David M, Palkovacs Eric P
Department of Ecology and Evolutionary Biology University of California Santa Cruz CA USA.
Southwest Fisheries Science Center National Marine Fisheries Service Santa Cruz CA USA.
Evol Appl. 2019 Nov 18;13(4):652-664. doi: 10.1111/eva.12890. eCollection 2020 Apr.
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 ( 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.
二次接触可能对生态和进化过程具有重要影响；然而，很少有研究从自然生态系统中二次接触开始就追踪其结果。我们评估了美国康涅狄格州罗杰斯湖的溯河产卵美洲西鲱重新引入项目，该湖中有一个因殖民时代筑坝而隔离的陆封型美洲西鲱种群。在恢复通往海洋的通道后，成年溯河产卵美洲西鲱被投放至湖中。我们评估了溯河产卵幼鱼的产量、基因渗入的程度和方向，以及生态型之间竞争的可能性。我们从恢复期间投放至湖中的所有成年美洲西鲱身上获取了鳍条样本，并在投放开始两年后从湖中产出的幼鱼中抽取了样本。我们使用分类赋值和系谱重建以及新开发的微单倍型遗传标记评估幼鱼的祖先。溯河产卵美洲西鲱成功在湖中产卵并与陆封型种群杂交。亲本溯源显示，雄性和雌性溯河产卵鱼对F1代杂交幼鱼的贡献相同。陆封回交后代的存在表明，一些杂交种在二次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，基因渗入似乎是从溯河产卵型向陆封型的定向过程。我们还检测到不同生境中不同生态型幼鱼估计丰度的差异，随着恢复工作的持续进行，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结果方面的效用。
