Effects of Parasites on the Structure and Dynamics of Food Webs

Abstract

Food web theory continues to be an important avenue of research in Ecology. Accounting for the diverse relationships between species in an ecosystem is fundamental to understanding how that system responds to the changing world we live in. Incorporating ever more diverse sets of species is vital to that goal and parasites are an important group of species that have yet to be wholly integrated with food web research. This dissertation provides three key insights into the roles that parasites play in food webs. First, by examining several empirical food webs, we show that though there are reliable structural differences between parasites and free living (that is, non-parasite) species at both the community and individual level, there are more similarities than differences. Second, we propose an extension to an existing structural model with parasites that is able to accurately capture structural properties of empirical food webs with parasites better than the Niche Model does. Finally, we examine the feasibility of incorporating parasites in existing allometric trophic network theory. We find that even when accounting for concomittant predation and a host-as-refuge effect, parasites are very disruptive when their metabolic rates are defined by standard metabolic theory.