Factors that mediate natural enemy impact on herbivore populations have important implications for both natural and managed ecosystems. One such factor, vegetation complexity, can enhance multiple-predator effects on prey by providing a refuge from intraguild predation, thereby enhancing herbivore suppression. Previous results indicate that in a salt-marsh system control of the planthopper Prokelisia dolus by its two major predators, the mirid Tytthus vagus and the wolf spider Pardosa littoralis, is enhanced in structurally-complex habitats. The mechanism underlying this increase in suppression is twofold: complex-habitats influence planthopper control directly through an increase in suppression by spiders alone, and indirectly via a reduction in the intraguild predation of mirids by spiders. This study aimed to elucidate the behavioral mechanisms underlying the differential susceptibility of planthoppers and mirids to spider predation in simple and complex habitats. Results from observational studies show that planthoppers are relatively sessile herbivores that feed for extended periods of time on cordgrass phloem. Therefore, in simple habitats planthoppers are inconspicuous to spiders. However, in complex habitats spiders use thatch as a scaffold to locate prey, increasing their encounter rate with planthoppers, and enhancing planthopper susceptibility. Alternatively, mirids are actively-foraging predators of planthopper eggs. Therefore, in simple habitats mirids are visually-apparent to wolf spiders and intraguild predation is frequent. However, thatch provides hiding sites and avenues of escape for mirids, decreasing their encounter rate with spiders, and rendering them less vulnerable to spider attack. Therefore, habitat complexity enhances predator effects on herbivores by mediating interactions between strict predators and prey as well as intraguild predators and intraguild prey. However, the outcomes of these interactions depend on species-specific behaviors of prey. Thus, elucidating behavioral mechanisms is essential to predicting the impact of habitat-mediated enemy effects on herbivore population dynamics.
Species 1: Hemiptera Delphacidae Prokelisia dolus (salt marsh planthopper)
Species 2: Araneae Lycosidae Pardosa littoralis (hunting spider)
Species 3: Hemiptera Miridae Tytthus vagus
Keywords: predator-predator interactions, predator-prey interactions
The ESA 2001 Annual Meeting - 2001: An Entomological Odyssey of ESA