Agricultural intensification drives landscape-context effects on host-parasitoid interactions in agroecosystems
Agricultural intensification drives landscape-context effects on host-parasitoid interactions in agroecosystems
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DOI：
10.1111/j.1365-2664.2012.02130.x
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发表时间：
2012-06-01
影响因子：
5.7
通讯作者：
Didham, Raphael K.
中科院分区：
文献类型：
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作者：
Jonsson, Mattias;Buckley, Hannah L.;Didham, Raphael K.
1.农业土地利用威胁生态系统服务，如生物控制的天敌，因为生境结构的简化和干扰和农用化学品投入的加剧。农业害虫的低寄生率通常归因于在高度简化的景观中缺乏寄生蜂资源，但这可能会被景观复杂性和集约化农业作物覆盖之间几乎无处不在的相关性所混淆。2.在这里，我们解开的机制，利用景观改造梯度，在景观中的栖息地类型和年度作物覆盖的多样性是不相关的驱动规模的影响hostparasitoid相互作用。我们量化了两个重要的作物害虫（蚜虫和小菜蛾）在30个景观的草食动物密度和寄生率和重寄生率。我们使用结构方程模型（SEM）来测试是否土地利用强度（杀虫剂的应用和栖息地干扰）或资源的可用性寄生虫（花卉资源和替代寄主植物）是介导的栖息地多样性和年度作物覆盖景观的影响。3.蚜虫的初次寄生率和重寄生率以及小菜蛾的初次寄生率随着年作物覆盖率的增加而降低，而景观中栖息地多样性的降低对寄生率的影响不大。这些影响几乎完全是由生境受到更大的干扰和杀虫剂使用频率增加引起的，而不是由资源供应的变化引起的。4.寄生蜂更敏感，集约化的耕作措施比他们的草食动物的主机，反过来hyperparasitoids更敏感，比主要的寄生蜂。这支持了理论预测，较高的营养水平应该是越来越敏感的干扰与土地利用变化。5.合成与应用。我们的工作表明，土地利用强度的增加（例如，更高的杀虫剂投入和更大程度的干扰与一年生作物面积的增加）已被低估的驱动程序的景观影响hostparasitoid相互作用。这些发现对维持生态系统服务，如生物控制具有重要意义。推广低强度耕作方法，限制农业化学品投入和生境干扰的程度和频率，对于维持农业生态系统中拟寄生虫的有效生物控制至关重要。
1. Agricultural land use threatens ecosystem services such as biological control by natural enemies because of simplification of habitat structure and intensification of disturbance and agrochemical inputs. Low parasitism rates of agricultural pests have typically been attributed to a lack of resources for parasitoids in highly simplified landscapes, but this could be confounded by the nearly ubiquitous correlation between landscape complexity and the cover of intensively farmed agricultural crops. 2. Here, we disentangle the mechanisms driving landscape-scale effects on hostparasitoid interactions by taking advantage of a landscape modification gradient in which the diversity of habitat types and annual crop cover in the landscape were uncorrelated. We quantified herbivore densities and parasitism and hyperparasitism rates on two important crop pests (aphids and Plutella xylostella) across 30 landscapes. We used structural equation modelling (SEM) to test whether land-use intensity (insecticide application and habitat disturbance) or resource availability for parasitoids (floral resources and alternative host plants) was mediating the effects of habitat diversity and annual crop cover on the landscape. 3. Rates of primary- and hyperparasitism of aphids and primary parasitism of P. xylostella decreased with increasing annual crop cover, whereas decreasing habitat diversity in the landscape had little effect on parasitism rates. These effects were mediated almost entirely by greater habitat disturbance and greater frequency of insecticide application, rather than by changes in resource availability. 4. Parasitoids were more sensitive to intensive farming practices than were their herbivore hosts, and in turn hyperparasitoids were more sensitive than were primary parasitoids. This supports the theoretical prediction that higher trophic levels should be increasingly sensitive to the disturbances associated with land-use change. 5. Synthesis and applications. Our work suggests that increased land-use intensity (e.g. higher insecticide inputs and greater levels of disturbance associated with increasing area of annual crops) has been underestimated as a driver of landscape effects on hostparasitoid interactions. These findings have important implications for the maintenance of ecosystem services such as biological control. The promotion of low-intensity farming practices that limit the extent and frequency of agrochemical inputs and habitat disturbances will be essential for the maintenance of effective biological control by parasitoids in agroecosystems.