Date of Award

2010

Degree Type

Dissertation

Department

Biological, Geological and Environmental Sciences

First Advisor

Tewari, Surendra

Subject Headings

Food webs, Food chains (Ecology), Forest ecology, Competition, Plethodon cinereus, Centipedes, Temperate forest floor, intraguild predator, trophic cascade

Abstract

High species diversity and complexity of forest-floor food webs present a challenge for understanding the role of species interactions (e.g. competition and predation) as regulatory mechanisms for ecosystem processes such as decomposition and nutrient cycling. In particular, we understand very little about the roles of forest-floor predators in regulating diversity and abundance of lower trophic levels and ecosystem processes. However, ecological theory and several studies suggest that interactions among intraguild predators (IGP) may be important controls of diversity and abundance of organisms and detritus in lower trophic levels within food webs. A key prediction is that interactions among predators weaken trophic cascades. My research examined this prediction by characterizing interactions among predators and examining their effects on lower trophic levels within the forest-floor food web of Northeast Ohio. The results of the laboratory microcosm studies, in combination with several previous studies, suggest that the effects of removal treatment on intraguild predators, especially centipedes, spiders, carabid beetles, and salamander, were not the result of intraguild predation, but were more likely to have been the result of non-consumptive competitive interactions (NCEs). Predator removal from open, unrestricted field plots resulted in changes in the abundances of several groups of predators and macrodetritivores. Additionally, I found that predator manipulation affected composition of microflora within the soils at my field site. The mechanisms for this effect remain uncertain but may be indicative of antibiotic interactions within the soil through bacteria dispersed through skin secretions and feces of predators, particularly salamanders. This work contributes significantly to a growing body of evidence indicating that territorial predators, such as P. cinereus, which are constrained to spatially fixed microhabitats, can be strong regulators of guild members and lower trophic levels. My results also suppo

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