Department of Ecology, Evolution, and Organismal Biology, 251 Bessey Hall, Iowa State University, Ames, Iowa 50011, USA.
Department of Biology, University of Washington, Seattle, Washington 98195, USA.
Nat Commun. 2017 Mar 8;8:14557. doi: 10.1038/ncomms14557.
Invasive vertebrate predators are directly responsible for the extinction or decline of many vertebrate species, but their indirect impacts often go unmeasured, potentially leading to an underestimation of their full impact. When invasives extirpate functionally important mutualists, dependent species are likely to be affected as well. Here, we show that the invasive brown treesnake, directly responsible for the extirpation of forest birds from the island of Guam, is also indirectly responsible for a severe decline in plant recruitment as a result of disrupting the fruit-frugivore mutualism. To assess the impact of frugivore loss on plants, we compare seed dispersal and recruitment of two fleshy-fruited tree species on Guam and three nearby islands with intact disperser communities. We conservatively estimate that the loss of frugivorous birds caused by the brown treesnake may have caused a 61-92% decline in seedling recruitment. This case study highlights the potential for predator invasions to cause indirect, pervasive and easily overlooked interaction cascades.
入侵的脊椎动物捕食者直接导致了许多脊椎动物物种的灭绝或减少，但它们的间接影响往往未被测量，这可能导致对其全面影响的低估。当入侵物种消灭了具有重要功能的共生伙伴时，依赖它们的物种也可能受到影响。在这里，我们表明，入侵的棕树蛇直接导致关岛森林鸟类灭绝，也间接地导致由于破坏了果实-传粉者共生关系，植物繁殖严重减少。为了评估传粉者丧失对植物的影响，我们比较了关岛和三个附近岛屿上两种肉质果实树种的种子传播和繁殖情况，这些岛屿上有完整的传播者群落。我们保守估计，棕树蛇导致的食果鸟类的丧失可能导致幼苗繁殖减少了 61-92%。这个案例研究强调了捕食者入侵可能导致间接、普遍且容易被忽视的相互作用级联的可能性。
