Habitat isolation moderates the strength of top-down control in experimental pond food webs
Habitat isolation moderates the strength of top-down control in experimental pond food webs
复制标题
DOI：
10.1890/09-0262.1
复制
发表时间：
2010-03-01
期刊：
影响因子：
4.8
通讯作者：
Biro, Elizabeth G.
中科院分区：
文献类型：
--
作者：
Chase, Jonathan M.;Bergett, Amber A.;Biro, Elizabeth G.
生境隔离会改变物种丰度、丰富度以及捕食者与猎物的比例，这是众所周知的。然而，隔离如何改变食物网内的相互作用则不太清楚。在此，我们展示了在人工池塘（中宇宙）中进行的一项实验结果，该实验对生境隔离以及捕食者减少处理进行了操作，以理清隔离如何调节捕食者自上而下的影响，即从捕食者经食草动物到生产者的营养级联强度。在连通的生境中，这种营养级联强度比在隔离的生境中要强得多。我们还发现，捕食者和食草动物物种的总体丰富度都随着隔离而大幅下降。对捕食者进行的实验性减少表明，食草动物反应的潜在机制可能是由关键捕食者效应介导的；当捕食者减少时，食草动物丰富度更低，并且隔离对食草动物丰富度没有明显影响。最后，我们发现，在更隔离的生境中，捕食者的组成包括体型更小且可能比在隔离程度较低的生境中持续存在的物种捕食效率更低的物种。总之，我们的实验表明，生境隔离可以通过相关物种的直接影响以及通过它们在食物网中的相互作用所介导的影响相结合的方式改变群落结构。
Habitat isolation is well known to alter patterns of species abundance, richness, and the ratios of predators: prey. Less clear, however, is how isolation alters interactions within food webs. Here, we present the results from an experiment performed in artificial ponds (mesocosms) manipulating habitat isolation crossed with a predator reduction treatment to disentangle how isolation mediates the top-down effect of predators. The strength of the trophic cascade, from predators, through herbivores, to producers. was considerably stronger in connected than in isolated habitats. We further found that the overall richness of both predator and herbivore species declined strongly with isolation. Experimental predator reductions suggest that the mechanism underlying the herbivore response was likely mediated by a keystone predator effect; when predators were reduced, herbivore richness was lower, and there was no discernable effect of isolation on herbivore richness. Finally, we found that the composition of predators in more isolated habitats consisted of species that were smaller and likely less effective predators than species that persisted in less isolated habitats. In all, our experiment showed that habitat isolation can alter the structure of communities by a combination of direct effects of the species in question. as well as effects mediated through their interactions in the food web.