Flathead Lake Biological Station, University of Montana, Polson, MT 59860;
Carterville Fish and Wildlife Conservation Office, US Fish and Wildlife Service, Wilmington, IL 60481.
Proc Natl Acad Sci U S A. 2021 Nov 9;118(45). doi: 10.1073/pnas.2102179118.
Species invasions can have substantial impacts on native species and ecosystems, with important consequences for biodiversity. How these disturbances drive changes in the trophic structure of native food webs through time is poorly understood. Here, we quantify trophic disruption in freshwater food webs to invasion by an apex fish predator, lake trout, using an extensive stable isotope dataset across a natural gradient of uninvaded and invaded lakes in the northern Rocky Mountains, USA. Lake trout invasion increased fish diet variability (trophic dispersion), displaced native fishes from their reference diets (trophic displacement), and reorganized macroinvertebrate communities, indicating strong food web disruption. Trophic dispersion was greatest 25 to 50 y after colonization and dissipated as food webs stabilized in later stages of invasion (>50 y). For the native apex predator, bull trout, trophic dispersion preceded trophic displacement, leading to their functional loss in late-invasion food webs. Our results demonstrate how invasive species progressively disrupt native food webs via trophic dispersion and displacement, ultimately yielding biological communities strongly divergent from those in uninvaded ecosystems.
物种入侵会对本地物种和生态系统造成重大影响，对生物多样性产生重要影响。然而，人们对于这些干扰如何随着时间的推移改变本地食物网的营养结构知之甚少。在这里，我们使用美国落基山脉北部一个从无入侵到有入侵的天然梯度的广泛稳定同位素数据集，量化了淡水食物网中由顶级鱼类捕食者——湖鳟入侵引起的营养中断。湖鳟的入侵增加了鱼类的饮食多样性（营养分散），使本地鱼类从其参考饮食中转移（营养置换），并重新组织了大型无脊椎动物群落，表明食物网受到了强烈的干扰。在殖民后 25 到 50 年内，营养分散最大，随着入侵后期食物网的稳定，营养分散逐渐消散（>50 年）。对于本地的顶级捕食者——虹鳟来说，营养分散先于营养置换，导致它们在后期入侵的食物网中功能丧失。我们的研究结果表明，入侵物种如何通过营养分散和置换逐渐破坏本地食物网，最终导致生物群落与未受干扰的生态系统有很大的差异。
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