Omnivory can both enhance and dampen perturbations in food webs

TL;DR

This paper analytically and numerically examines how omnivory and self-interaction influence the stability of food webs, revealing that they can both dampen and enhance perturbations depending on their position and interactions.

Contribution

It provides a unified analytical framework showing that omnivory and intraspecific competition can either stabilize or destabilize food webs, clarifying their roles in ecological stability.

Findings

Intraspecific competition can dampen or enhance perturbations.

Omnivory's effect on stability depends on its position in the food web.

Results support both sides of the debate on omnivory's role in stability.

Abstract

We investigate how perturbations propagate up and down a food chain with and without self-interaction and omnivory. A source of perturbation is a shift in death rate of a trophic level, and the measure of perturbation is the difference between the perturbed and unperturbed steady state populations. For Lotka-Volterra food chains with linear functional response, we show analytically that both intraspecific competition and intraguild predation can either dampen or enhance the propagation of perturbations, thus stabilizing or destabilizing the food web. The direction of the effect depend on the position of the source of perturbation, as well as on the position of the additional competitive and predatory links . These conclusions are confirmed numerically for a food chain with more realistic Type-II functional response. Our results support the positions of both sides in the long-standing debate on the effect of intraspecific competition and omnivory on the stability of trophic systems.