Spatial Subsidy of an Intraguild Predator: Consequences for Top-down and Bottom-up Impacts on Insect Herbivores

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Spatial subsidy of an intraguild predator:consequences for top-down and bottom-up impacts on insect herbivoresThe research herein proposes to extend our work on natural enemy versus host plant control of insect herbivores (planthoppers) inhabiting the Spartina alterniflora salt marshes along the Atlantic coast to include the effects of an extensive spatial subsidy of intraguild predators (Pardosa wolf spiders) from a neighboring upland system (Spartina patens). Specifically, spatially dependent hypotheses are tested concerning the impact of this annual predator subsidy as it interfaces with spatial variation in vegetation structure on planthopper dynamics, food-web interactions, and the probability for trophic cascades in Spartina alterniflora. As natural habitats become more fragmented and the exchange of players among systems increases, it becomes imperative to understand the consequences of such predator incursions on food-web dynamics and local biodiversity. Also, elucidating the consequences of predator subsidies on insect herbivores has important implications for agriculture. For example, pest managers are now seeking ways to encourage natural enemies and promote pest suppression in cropping systems by establishing "spatial refuges" for predators in neighboring habitats. Thus, gaining insight into factors that promote the exchange of predators between different habitats may lead to more effective pest management strategies in a world of mandated pesticide reduction.