1. Esox lucius L. (northern pike) inhabits river, lake, and brackish water ecosystems of the temperate region in North America and Eurasia. In many areas of its native range, the species is confronted with human‐induced disturbances that can affect local and regional genetic diversity. Conservation of genetic diversity constitutes an important policy objective. Therefore, we investigated how the genetic population structure and patterns suggestive of hybridisation among subpopulations from different catchments vary with the type of ecosystem (river vs. lake) and the integrity of the ecosystem assessed using ecological status assessments of the European Water Framework Directive and indices of the wetland quality (in rivers) and trophic state (in lakes).
2. In total, 1,384 pike samples from the North, Baltic, and Black Sea drainages in Germany were analysed. We differentiated between metapopulations from each hydrogeographic region using genotypes from 15 microsatellites and mitochondrial cyt b sequences.
3. Individual populations showed signs of genetic admixture ranging from almost zero to complete replacement by foreign genotypes originating from different catchments. Hierarchical general linear modelling revealed a significantly positive association of the degree of genetic hybridisation with decreasing ecological status. An eroded population substructure indicative of hybridisation was also significantly elevated in rivers relative to lakes and in heavily modified water bodies. Results were consistent when using ecological status assessments by the Water Framework Directive and an alternative environmental quality index based on the health of wetlands in rivers and trophic state in lakes.
4. We speculate that macrophyte loss through loss of wetlands or in response to eutrophication fostered genetic mixing among different subpopulations, which were brought into secondary contact either due to stocking or due to natural dispersal from foreign catchments. Our findings suggest that anthropogenic alteration of freshwater ecosystems may influence the genetic structures present in a freshwater top piscivore at both local and regional scales.

中文翻译：

---

淡水生态系统的人为改变导致的顶级掠食性鱼类（北梭鱼，Esox lucius）的遗传种群结构

1. Esox lucius L.（北派克）栖息于北美和欧亚大陆温带地区的河流，湖泊和微咸水生态系统中。在其本土范围的许多地区，该物种都面临着人为干扰，可能会影响当地和区域的遗传多样性。保护遗传多样性是一项重要的政策目标。因此，我们调查了暗示不同流域亚种群之间杂交的遗传种群结构和模式如何随生态系统类型（河流与湖泊）以及使用欧洲水框架指令和指数的生态状况评估而评估的生态系统完整性而变化的湿地质量（在河流中）和营养状态（在湖泊中）。
2. 总共分析了德国北部，波罗的海和黑海排水系统中的1,384个派克样本。我们使用来自15个微卫星和线粒体cyt b序列的基因型来区分每个水文地理区域的种群。
3. 个别人群显示出遗传混合的迹象，从几乎零到完全被来自不同流域的外源基因型替代。层次通用线性建模揭示了遗传杂交程度与生态状况下降的显着正相关。相对于湖泊和经过大量改造的水体，指示杂交的受侵蚀的种群子结构也显着升高。当使用《水框架指令》的生态状况评估和基于河流湿地健康状况以及湖泊营养状态的替代环境质量指数时，结果是一致的。
4. 我们推测由于湿地的丧失或对富营养化的响应而导致大型植物的丧失促进了不同亚种群之间的遗传混合，这些亚种群由于种群或由于外国流域的自然扩散而成为次生接触。我们的发现表明，人为改变淡水生态系统可能会影响本地和区域规模的淡水食肉动物的遗传结构。