Invasive vertebrates are frequently reported to have catastrophic effects on the populations of species which they directly impact. It follows then, that if invaders exert strong suppressive effects on some species then other species will indirectly benefit due to ecological release from interactions with directly impacted species. However, evidence that invasive vertebrates trigger such trophic cascades and alter community structure in terrestrial ecosystems remains rare. Here, we ask how the cane toad, a vertebrate invader that is toxic to many of Australia's vertebrate predators, influences lizard assemblages in a semi-arid rangeland. In our study area, the density of cane toads is influenced by the availability of water accessible to toads. We compared an index of the abundance of sand goannas, a large predatory lizard that is susceptible to poisoning by cane toads and the abundances of four lizard families preyed upon by goannas (skinks, pygopods, agamid lizards, and geckos) in areas where cane toads were common or rare. Consistent with the idea that suppression of sand goannas by cane toads initiates a trophic cascade, goanna activity was lower and small lizards were more abundant where toads were common. The hypothesis that suppression of sand goannas by cane toads triggers a trophic cascade was further supported by our findings that small terrestrial lizards that are frequently preyed upon by goannas were more affected by toad abundance than arboreal geckos, which are rarely consumed by goannas. Furthermore, the abundance of at least one genus of terrestrial skinks benefitted from allogenic ecosystem engineering by goannas where toads were rare. Overall, our study provides evidence that the invasion of ecosystems by non-native species can have important effects on the structure and integrity of native communities extending beyond their often most obvious and frequently documented direct ecological effects.

中文翻译：

---

由侵入性脊椎动物引发的营养级联改变了天然爬行动物群落的结构。

据报道，侵入性脊椎动物对其直接影响的物种种群具有灾难性影响。随之而来的是，如果入侵者对某些物种产生强大的抑制作用，那么其他物种将由于与直接受影响物种相互作用的生态释放而间接受益。然而，很少有证据表明侵入性脊椎动物会触发这种营养级联反应并改变陆地生态系统中的群落结构。在这里，我们问甘蔗蟾蜍（一种对澳大利亚许多脊椎动物掠食者有毒的脊椎动物入侵者）如何影响半干旱牧场中的蜥蜴组合。在我们的研究区域，甘蔗蟾蜍的密度受蟾蜍可获取的水的可用性影响。我们比较了沙鹅的数量指数，大型掠食性蜥蜴，在甘蔗蟾蜍常见或罕见的地区，它们容易被甘蔗蟾蜍毒死，并且容易被甘纳（s 、,、蜥蜴和壁虎）捕食的四个蜥蜴科丰富。与甘蔗蟾蜍抑制沙go鹅引发营养级联的想法一致，在蟾蜍常见的地方，go鹅活动性较低，而小蜥蜴则更为丰富。我们的发现进一步证实了甘蔗蟾蜍抑制沙go虫营养级联的假说，即go虫经常捕食的小型陆生蜥蜴比ar虫壁虎更容易受到蟾蜍丰度的影响，而壁虎很少被go虫消耗。此外，至少有一个属的陆生石龙子受益于蟾蜍稀有的甘那人的异体生态系统工程。总体而言，我们的研究提供了证据，表明非本地物种对生态系统的入侵可能会对本地社区的结构和完整性产生重要影响，而不仅仅是其最明显和经常被记录的直接生态影响。