The alteration of structural connectivity in fluvial networks is important for the genetic dynamics of aquatic species. Exploring the effects of network fragmentation through genetic analysis is crucial to assess the conservation status of riverine species. In this study, we investigated the genetic consequences of the altered connectivity of brown trout in the Deva–Cares catchment (northern Spain). We investigated (1) genetic diversity, (2) genetic differentiation and genetic structure, (3) migration rates and effective population size and (4) genetic differentiation and riverscape characteristics. Analysis of the genetic variation among 197 individuals from the 13 study sites revealed a high degree of genetic differentiation (F_ST = 0.181). Below-barrier study sites had higher genetic diversity and lower F_ST values, while headwater and above-barrier study sites had lower genetic diversity and higher F_ST values. Most of the genetic groups identified were separated by one or more impermeable barriers. We reported an abrupt decrease in genetic diversity and effective population size in upper course tributaries and isolated reaches. Likewise, a downstream-biased gene flow was found, and it was most likely related to the fragmentation caused by barriers, since the results from migration indicated that gene flow between groups without impermeable barriers was higher bidirectionally. Isolation by impermeable barriers played a more important role than hydrological distance in determining the genetic structure. Most of the genetic groups showed small effective population sizes. Genetic analysis at the river network scale provides evidence for the role of barriers in determining genetic diversity patterns, highlighting the importance of maintaining and restoring river longitudinal connectivity.

河流网络结构连通性的改变对于水生物种的遗传动态很重要。通过遗传分析探索网络碎片化的影响对于评估河流物种的保护状况至关重要。在这项研究中，我们调查了 Deva-Cares 流域（西班牙北部）褐鳟连接性改变的遗传后果。我们调查了（1）遗传多样性，（2）遗传分化和遗传结构，（3）迁移率和有效种群规模以及（4）遗传分化和河景特征。对来自 13 个研究地点的 197 个个体的遗传变异进行分析，揭示了高度的遗传分化（F _ST = 0.181)。屏障下研究地点具有较高的遗传多样性和较低的F _ST值，而源头和屏障以上研究地点具有较低的遗传多样性和较高的F _ST值价值观。鉴定出的大多数基因组被一个或多个不可渗透的屏障隔开。我们报告了上游支流和孤立河段的遗传多样性和有效种群规模突然下降。同样，发现了一种下游偏向的基因流动，这很可能与障碍引起的片段化有关，因为迁移的结果表明，没有不可渗透障碍的组之间的基因流动双向更高。在确定遗传结构方面，不透水屏障的隔离比水文距离更重要。大多数遗传组显示出较小的有效种群规模。河网规模的遗传分析为障碍在确定遗传多样性模式中的作用提供了证据，