Trophic Cascades and Interacting Control Processes in a Detritus-based Terrestrial Food Web

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WiseDEB 9815842Terrestrial ecosystems typically contain species-rich assemblages of generalist predators. These predators not only prey upon lower trophic levels but also on other species of generalist predators, an interaction known as intraguild predation (IGP). These complex feeding connections are anticipated to blur distinctions between trophic levels and lead to the prediction that changes in abundances of generalist predators should have minimal effects on species at the base of food webs. As a consequence, it has been anticipated that trophic cascades should be weak in terrestrial food webs with high IGP. This research project will test this hypothesis in a series of field experiments manipulating spiders in the detritus-based food webs of forest-floor leaf litter. Cursorial and web-building spiders will be enhanced or decreased in one series of experiment to test if predation on detritivores by spiders initiates trophic cascades that affect the rates at which leaf litter decomposes. A second set of experiments will manipulate densities of detritivores and arthropod predators of the wolf spider to determine if resource limitation is more influential than IGP on the population dynamics of an abundant generalist predator. This research will increase ecological understanding of trophic structure, control processes and indirect effects in a common and important terrestrial food web.