Colman N J, Gordon C E, Crowther M S, Letnic M
Hawkesbury Institute for the Environment, University of Western Sydney, , Locked Bag 1797, Penrith, New South Wales 2751, Australia, School of Biological Sciences, University of Sydney, , Sydney, New South Wales 2006, Australia, Centre for Ecosystem Science, University of New South Wales, , Sydney, New South Wales 2052, Australia, School of Biological, Earth and Environmental Sciences, University of New South Wales, , Sydney, New South Wales 2052, Australia.
Proc Biol Sci. 2014 Mar 11;281(1782):20133094. doi: 10.1098/rspb.2013.3094. Print 2014 May 7.
Disruption to species-interaction networks caused by irruptions of herbivores and mesopredators following extirpation of apex predators is a global driver of ecosystem reorganization and biodiversity loss. Most studies of apex predators' ecological roles focus on effects arising from their interactions with herbivores or mesopredators in isolation, but rarely consider how the effects of herbivores and mesopredators interact. Here, we provide evidence that multiple cascade pathways induced by lethal control of an apex predator, the dingo, drive unintended shifts in forest ecosystem structure. We compared mammal assemblages and understorey structure at seven sites in southern Australia. Each site comprised an area where dingoes were poisoned and an area without control. The effects of dingo control on mammals scaled with body size. Activity of herbivorous macropods, arboreal mammals and a mesopredator, the red fox, were greater, but understorey vegetation sparser and abundances of small mammals lower, where dingoes were controlled. Structural equation modelling suggested that both predation by foxes and depletion of understorey vegetation by macropods were related to small mammal decline at poisoned sites. Our study suggests that apex predators' suppressive effects on herbivores and mesopredators occur simultaneously and should be considered in tandem in order to appreciate the extent of apex predators' indirect effects.
顶级食肉动物灭绝后，食草动物和中型食肉动物数量激增导致物种互动网络遭到破坏，这是全球生态系统重组和生物多样性丧失的一个驱动因素。大多数关于顶级食肉动物生态作用的研究都集中在它们与食草动物或中型食肉动物单独互动所产生的影响上，却很少考虑食草动物和中型食肉动物的影响是如何相互作用的。在此，我们提供证据表明，对一种顶级食肉动物——澳洲野狗进行致死控制所引发的多条级联路径，导致了森林生态系统结构的意外变化。我们比较了澳大利亚南部七个地点的哺乳动物群落和林下植被结构。每个地点都包括一个对澳洲野狗进行投毒的区域和一个未进行控制的区域。对澳洲野狗的控制对哺乳动物的影响与体型大小相关。在对澳洲野狗进行控制的地方，食草性有袋动物、树栖哺乳动物以及一种中型食肉动物——赤狐的活动更为频繁，但林下植被更为稀疏，小型哺乳动物的数量也更少。结构方程模型表明，在投毒地点，狐狸的捕食以及有袋动物对林下植被的消耗都与小型哺乳动物数量的减少有关。我们的研究表明，顶级食肉动物对食草动物和中型食肉动物的抑制作用是同时发生的，为了全面了解顶级食肉动物的间接影响程度，应该将二者结合起来考虑。
