Food webs for parasitologists: a review.

This review examines the historical origins of food web theory and explores the reasons why parasites have traditionally been left out of food web studies. Current paradigms may still be an impediment because, despite several attempts, it remains virtually impossible to retrofit parasites into food web theory in any satisfactory manner. It seems clear that parasitologists must return to first principles to solve how best to incorporate parasites into ecological food webs, and a first step in changing paradigms will be to include parasites in the classic ecological patterns that inform food web theory. The limitations of current food web models are discussed with respect to their logistic exclusion of parasites, and the traditional matrix approach in food web studies is critically examined. The well-known energetic perspective on ecosystem organization is presented as a viable alternative to the matrix approach because it provides an intellectually powerful theoretical paradigm for generating testable hypotheses on true food web structure. This review proposes that to make significant contributions to the food web debate, parasitologists must work from the standpoint of natural history to elucidate patterns of biomass, species abundance, and interaction strengths in real food webs, and these will provide the basis for more realistic models that incorporate parasite dynamics into the overall functional dynamics of the whole web. A general conclusion is that only by quantifying the effects of parasites in terms of energy flows (or biomass) will we be able to correctly place parasites into food webs.