Parasites can make significant contributions to ecosystem structure. However, most published food webs do not include information on parasites. Our understanding of the role of parasites in food webs is largely restricted to temperate estuarine systems. To expand our understanding of the general role of parasites in ecosystems, we have assembled a series of novel food webs using consistent methods, which allows us to place parasites on the same empirical footing as free-living consumers. These food webs span marine, intertidal, terrestrial, and freshwater systems, from the equator to the Arctic Circle. We compare free-living and infectious consumers in these systems in terms of their diversity, biomass, and impact on network structure.
Results/Conclusions
Because infectious consumers can comprise one-third of the species in systems, they make important contributions to diversity and biomass. Furthermore, infectious consumer strategies and life histories enmesh them into food webs in ways that are quantitatively different from free-living consumers. For example, parasite species feed across a much broader range of resource body-sizes than is typical of free-living consumers. Because parasites favor different consumer strategies and transmission methods in terrestrial environments than in aquatic environments, their integration into food webs differs in terrestrial compared to aquatic ecosystems.