Dormancy stabilizes structured food webs

Abstract

Theory predicts that strong species interactions drive ecological instability, but strong interactions are common in ecosystems while strong instability appears rare. This discrepancy motivates enduring interest in ecological mechanisms that limit or counteract instability. Dormancy - reversible metabolic suppression - may be one. Dormancy is a ubiquitous life history trait found in organisms ranging from bacteria to trees. Dormant individuals form "seed banks" that are temporarily disengaged from demographic processes and species interactions, creating a memory of past ecological dynamics. Seed banks can stabilize predator-prey interactions, but whether, when, and how they affect the stability of larger ecological networks is uncertain. We show that dormancy stabilizes oscillatory dynamics in a minimal mathematical model and illustrate how dormancy converts high oscillation frequency into strong restoring force. We find that dormancy can have qualitative stabilizing effects in structured food webs that undergo Hopf bifurcations and exhibit oscillatory instability, but not in unstructured networks or those dominated by competitive or mutualistic interactions. This classification remains accurate when only a subset of species go dormant and drive stabilization. Our results clarify when dormancy can promote stability, indicating that dormancy may be an important but overlooked stabilizing factor in food webs.