Multi-scale herbivore regulation in agroecosystems: role of multiple predator assemblages and bottom-up controls

有益的昆虫提供重要的生态系统服务，控制昆虫食草动物(害虫)，每年可节省数十亿美元。然而，天敌用来控制害虫的许多基本机制知之甚少，尽管存在自然控制剂，但害虫种群经常达到暴发水平。食草动物种群受多种空间尺度上的因子调控。在景观尺度上，自然栖息地和农田可能成为攻击农业害虫的有益昆虫的来源。以前的研究表明，景观的几个特征会影响天敌控制害虫的效果，包括自然植被的范围、农田的大小以及其他作物是否靠近有益昆虫的栖息地。然而，农业领域害虫和天敌之间发生的相互作用的类型也决定了害虫抑制的水平。相互作用可能包括：1)田间植物作为害虫的食物来源的影响；2)不同天敌之间的相互作用，这可能导致更高(更有效)或更低(天敌之间的干扰)的害虫抑制。我计划在商业领域进行一系列实验，以测试1)在拥有不同程度有益昆虫的景观中，当地因素对害虫控制的影响程度，2)景观中导致有益昆虫对害虫抑制水平更高的特征，以及3)天敌组合最有效地抑制害虫。从理论角度来看，这些实验将为在多个尺度上调节昆虫食草动物提供新的见解。从更实用的角度来看，这项研究的结果将使我们能够专注于在农业景观中有效地抑制害虫的天敌群体，保护和加强天然害虫防治剂提供的生态系统服务，并通过传统做法减少目前的杀虫剂负荷和相关的环境成本。

Beneficial insects provide important ecosystem services controlling insect herbivores (pests) that result in savings of billions of dollars per year. However, many of the basic mechanisms that natural enemies use to control pests are poorly understood and pest populations frequently reach outbreak levels despite the presence of natural control agents. Herbivore populations are regulated by factors operating at multiple spatial scales. At the landscape scale, natural habitats and crop land may act as sources of beneficial insects that attack agricultural pests. Previous studies have shown that several features of the landscape influence the effectiveness of pest control by natural enemies, including extent of natural vegetation, agricultural field size, and the proximity of other crops that harbor beneficial insects. However, the type of interactions taking place between pests and natural enemies in an agricultural field also determines the level of pest suppression. Interactions may include: 1) effects of the plants in a field as a food sources for pests, and 2) interactions among different natural enemies, that could result in both higher (more efficient) or lower (interference among natural enemies) pest suppression. I plan to conduct a series of experiments in commercial fields to test 1) the extent to which local factors affect pest control in landscapes that harbor varying levels of beneficial insects, 2) the features in the landscape that result in higher levels of pest suppression by beneficial insects, and 3) the combinations of natural enemies most effective at suppressing pests. From a theoretical perspective, these experiments will provide new insights into the regulation of insect herbivores at multiple scales. From a more applied perspective, the results of this research will allow us to focus on groups of natural enemies that are effective at suppressing pests in agricultural landscapes, to conserve and enhance the ecosystem service provided by natural pest control agents, and to reduce the current pesticide load and associated environmental cost of managing insect pests through conventional practices.