Effects of "Bottom-Up", "Lateral", and "Top-Down" Forces on the Structure of a Phytophagous Insect Community

9527846否认植食性(以植物为食)昆虫的植物特性(“自下而上”)和天敌(“自上而下因素”)在种群和群落生态中的相对重要性几十年来一直存在争议。再加上竞争(“横向因素”)对食草性昆虫群落的影响，这个问题变得更加复杂。到目前为止，很少有研究确定：(1)“自下而上”、“横向”和“自上而下”的力量是否协调一致；(2)这些力量之间存在重要的相互作用；(3)每个食草动物物种都受到不同因素的影响，以至于没有单一的力量决定群落的组织。本研究采用控制寄主植物质量、竞争和捕食的实验方法，以了解影响北美东部潮间带沼泽植食性昆虫群落的因素。主要的生物是盐沼绳草，它的主要食汁性昆虫，以及它们的主要捕食者，捕食蜘蛛。现有证据表明，“自下而上”、“横向”和“自上而下”的力量在这个系统中都是潜在的重要力量，每个食草动物物种对这些力量的反应是不同的。因此，这个系统提供了一个令人兴奋的机会来评估这些力量是如何整合在一起来确定每个草食动物物种的丰度的。这项拟议的研究将对揭开在决定植物食性昆虫的分布和丰度方面影响最大的相互作用做出重大贡献。将研究的敏感湿地生态系统与水稻、玉米和甘蔗等许多农业种植制度惊人地相似。相似性包括栖息地的一致性，以及草食性昆虫及其天敌的类型。这项研究的结果将提供关于寄主植物因素(肥料制度和品种抗性)和生物防治因素的重要性以及它们如何相互作用以抑制农业害虫种群的迫切需要的信息。

9527846 Denno The relative importance of plant characteristics ("bottom-up") and natural enemies ("top-down factors") in the population and community ecology of phytophagous (plant-feeding) insects has been disputed for decades. Add to this the effects of competition ("lateral factors") on herbivorous insect communities and the issue becomes more complicated. To date, very few studies have determined whether: (1) "bottom-up", "lateral", and "top-down" forces act in concert, (2) important interactions exist among these forces, and (3) each herbivore species is influenced by different factors such that no single force dictates community organization. The present research employs an experimental approach in which host plant quality, competition, and predation are manipulated to understand the factors which influence the plant-feeding insect community in intertidal marshes of eastern North America. The major organisms are salt marsh cord grass, its dominant sap-feeding insects, and their major predators, hunting spiders. Existing evidence suggests that "bottom-up", "lateral", and "top-down" forces are all potentially important in this system, and that each herbivore species responds to these forces differently. Thus, this system provides the exciting opportunity to assess how these forces integrate to determine the abundance of each herbivore species. The proposed research will make a significant contribution toward unraveling the interactions most influential in dictating the distribution and abundance of plant-feeding insects. The sensitive wetland ecosystem that will be studied is strikingly similar to many agricultural cropping systems such as rice, corn, and sugar cane. Similarities include the uniformity of the habitat, as well as the types of herbivorous insects and their natural enemies. The results of this study will provide critically-needed information on the importance of host-plant factors (fertilizer regimes and varietal resistance) and biological control agents and how they interact to suppress agricultural pest populations.