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.
