In the absence of mammals, the fauna of islands is characterised by high endemism levels and a tendency towards gigantism, flightlessness and longevity. These characteristics have resulted in a high vulnerability to introduced animals, either directly via predation or indirectly through an alteration of food web interactions. Because invertebrates are important components of food webs and essential for many ecosystem processes, we investigated how different mammal and bird communities, present inside and outside a fenced reserve, influenced ground-dwelling invertebrates on the mainland of New Zealand. Some significant differences in invertebrate community composition were apparent inside versus outside the fenced reserve, predominantly Ctenognathus adamsi (Carabidae) being twenty times more abundant inside the reserve, and rove beetles (Staphylinidae) being eight times more abundant outside the reserve. The introduced blackbird (Turdus merula) was observed more regularly than other predators of invertebrates outside the reserve, while native robins (Petroica longipes) were more highly detected inside the reserve. Despite differences in the vertebrate insectivore community outside the reserve (multiple mammals and introduced birds) compared to inside (mainly native birds), the resulting similarity in net predation pressure may explain the apparent similarity in abundance for most of the other 24 invertebrate taxa examined. Removal of most mammals from within fenced reserves in New Zealand may enable introduced and native birds to flourish, with flow-on effects on the invertebrate community. We conclude that further study of trophic interactions and additional intervention, may need to be considered if invertebrate conservation is a desired outcome from fenced reserves.

中文翻译：

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哺乳动物排斥对新西兰无脊椎动物群落的影响

在没有哺乳动物的情况下，岛屿动物群的特点是地方性高，并且趋向于巨大、不会飞和长寿。这些特征导致对引入动物的高度脆弱性，无论是直接通过捕食还是间接通过改变食物网相互作用。由于无脊椎动物是食物网的重要组成部分，对许多生态系统过程至关重要，因此我们调查了围栏保护区内外的不同哺乳动物和鸟类群落如何影响新西兰大陆的地栖无脊椎动物。围栏保护区内外的无脊椎动物群落组成存在明显差异，主要是Ctenognathus adamsi(Carabidae) 在保护区内的数量是其 20 倍，而在保护区外，鲹 (Staphylinidae) 的数量是其 8 倍。引入的黑鸫（Turdus merula）比保护区外的其他无脊椎动物捕食者更经常地被观察到，而本地知更鸟（Petroica longipes）在保护区内被更频繁地检测到。尽管保护区外的脊椎动物食虫群落（多种哺乳动物和引进的鸟类）与内部（主要是本地鸟类）相比存在差异，但由此产生的净捕食压力可以解释所检查的其他 24 种无脊椎动物类群中的大多数在丰度上的明显相似性。从新西兰的围栏保护区内移除大多数哺乳动物可能会使引进和本地鸟类繁衍生息，对无脊椎动物群落产生流动影响。我们得出的结论是，如果无脊椎动物保护是围栏保护区的理想结果，则可能需要考虑进一步研究营养相互作用和额外干预。