Spillover of agriculturally subsidized predators as a potential threat to native insect herbivores in fragmented landscapes
Spillover of agriculturally subsidized predators as a potential threat to native insect herbivores in fragmented landscapes
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DOI：
10.1111/j.1523-1739.2006.00507.x
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发表时间：
2006-12-01
影响因子：
6.3
通讯作者：
Louda, Svata A.
中科院分区：
文献类型：
--
作者：
Rand, Tatyana A.;Louda, Svata A.
栖息地丧失和破碎化可能对一些本地物种的种群产生强烈的负面影响。周围景观基质中的通才天敌的溢出是一种可能产生这种效应的机制，但这在昆虫中很少被研究。我们研究了栖息地转变为农业对捕食性瓢虫丰度的影响以及对美国内布拉斯加州中部 12 个草原残余物中本地昆虫食草动物的潜在影响。扫描采样结果显示，在三年的研究中，与以草地为主的景观中的对照地点相比，在以农田为主的景观中的原生草地地点，瓢虫的数量要多三到六倍。排除实验进一步表明，捕食强度与不同地点的瓢虫丰度密切相关，并且瓢虫可以显着降低本地蚜虫食草动物的密度。与专门昆虫寄生蜂的研究相比，这些研究通常发现破碎的景观中敌人的压力减少，我们的结果表明，在某些情况下，由于来自周围农田栖息地的通才捕食者的溢出，本地食草动物可能会在栖息地丧失增加的景观中经历更大的消费压力。
Habitat loss and f\ragmentation can have strong negative impacts on populations of some native species. Spillover of generalist natural enemies from the surrounding landscape matrix is one mechanism potentially generating such effects, yet this has been rarely studied in insects. We examined the influence of habitat conversion to agriculture on the abundance and potential effects of predatory coccinellid beetles on native insect herbivores within 12 grassland remnants in central Nebraska (U.S.A.). Results of sweep sampling revealed that coccinellids were three to six times more abundant at native grassland sites embedded within cropland-dominated landscapes compared with control sites in grassland-dominated landscapes over the 3 years of the study. Exclusion experiments further demonstrated that predation intensity was strongly related to coccinellid abundances across sites and that coccinellids can dramatically reduce densities of a native aphid herbivore. In contrast to studies of specialized insect parasitoids, which have generally found reduced enemy pressure in fragmented landscapes, our results suggest that native herbivores may in some cases experience increased consumer pressure in landscapes with increasing habitat loss because of spillover of generalist predators from surrounding cropland habitats.