ESE, Ecology and Ecosystem Health, INRAE, Agrocampus Ouest, 35042, Rennes, France.
Département de biologie, Institut de Biologie Intégrative etsu des Systèmes (IBIS), Université Laval, Québec, G1V 0A6, Canada.
Heredity (Edinb). 2021 Feb;126(2):235-250. doi: 10.1038/s41437-020-00367-9. Epub 2020 Sep 28.
Understanding the effect of human-induced landscape fragmentation on gene flow and evolutionary potential of wild populations has become a major concern. Here, we investigated the effect of riverscape fragmentation on patterns of genetic diversity in the freshwater resident European brook lamprey (Lampetra planeri) that has a low ability to pass obstacles to migration. We tested the hypotheses of (i) asymmetric gene flow following water current and (ii) an effect of gene flow with the closely related anadromous river lamprey (L. fluviatilis) ecotype on L. planeri genetic diversity. We genotyped 2472 individuals, including 225 L. fluviatilis, sampled from 81 sites upstream and downstream barriers to migration, in 29 western European rivers. Linear modelling revealed a strong positive relationship between genetic diversity and the distance from the river source, consistent with expected patterns of decreased gene flow into upstream populations. However, the presence of anthropogenic barriers had a moderate effect on spatial genetic structure. Accordingly, we found evidence for downstream-directed gene flow, supporting the hypothesis that barriers do not limit dispersal mediated by water flow. Downstream L. planeri populations in sympatry with L. fluviatilis displayed consistently higher genetic diversity. We conclude that genetic drift and slight downstream gene flow drive the genetic make-up of upstream L. planeri populations whereas gene flow between ecotypes maintains higher levels of genetic diversity in L. planeri populations sympatric with L. fluviatilis. We discuss the implications of these results for the design of conservation strategies of lamprey, and other freshwater organisms with several ecotypes, in fragmented dendritic river networks.
理解人类活动导致的景观破碎化对野生种群基因流动和进化潜力的影响已成为一个主要关注点。在这里，我们研究了河景破碎化对淡水定居型欧洲七鳃鳗（Lampetra planeri）遗传多样性模式的影响，这种鱼类的迁移能力很低，难以穿越障碍物。我们检验了以下两个假说：（i）水流引起的不对称基因流动，以及（ii）与洄游型河流七鳃鳗（L. fluviatilis）生态型密切相关的基因流动对 L. planeri 遗传多样性的影响。我们对 29 条西欧河流中 81 个迁移障碍上下游的 2472 个个体进行了基因分型，包括 225 个 L. fluviatilis。线性模型表明，遗传多样性与河流源头的距离呈强烈的正相关，这与预期的基因流入上游种群减少的模式一致。然而，人为障碍物的存在对空间遗传结构有中等程度的影响。因此，我们发现了下游基因流动的证据，支持了障碍物不会限制水流介导的扩散的假说。与 L. fluviatilis 同域分布的下游 L. planeri 种群表现出更高的遗传多样性。我们得出的结论是，遗传漂变和轻微的下游基因流动驱动了上游 L. planeri 种群的遗传构成，而生态型之间的基因流动维持了与 L. fluviatilis 同域分布的 L. planeri 种群更高水平的遗传多样性。我们讨论了这些结果对在支状河流网络中保护七鳃鳗和其他具有多种生态型的淡水生物的策略的影响。
