REEVALUATING THE OMNIVORY-STABILITY RELATIONSHIP IN FOOD WEBS

Under equilibrium conditions, previous theory has shown that the prese nce of omnivory destabilizes food webs. Correspondingly, omnivory ough t to be rare in real food webs. Although early food-web data appeared to verify this, recently many ecologists have found omnivory to be ubi quitous in food-web data gathered at a high taxonomic resolution. In t his paper, we reinvestigate the role of omnivory in food webs using a non-equilibrium perspective. We find that the addition of omnivory to a simple food-chain model (thus a simple food web) locally stabilizes the food web in a very complete way. First, non-equilibrium dynamics ( e.g. chaos) tend to be eliminated or bounded further away from zero, v ia period-doubling reversals invoked by the omnivorous trophic link. S econd, food chains without interior attractors tend to gain a stable i nterior attractor with moderate amounts of omnivory.