How can dispersal-induced asymmetry and asynchrony support the coexistence of species?

The survival of species in fragmented landscapes depends crucially on their dispersal ability, which enables them to colonize new spatial patches with better resource conditions, thereby enhancing population stability against extinction. We study how dispersal of different classes of species shape the long-term coexistence in dispersal-coupled three-trophic food webs containing plants, herbivores, and carnivores. Our focus is on the interplay between non-equilibrium dynamics (periodic and chaotic) and dispersal in maintaining the coexistence of all species in the ecosystem under changing environmental conditions. We distinguish between plant and animal dispersal to reflect different ecological situations. Using carrying capacity as the control parameter, we combine bifurcation analysis with long integrations and identify two coexisting dynamical regimes over overlapping parameter ranges: a carnivore-free limit cycle and different chaotic attractors supporting the coexistence of all species. We show that, in environmentally identical patches, dispersal can support persistence through a specific nonlinear dynamical route: (1) by generating dispersal-induced multistability between carnivore-free oscillations and various chaotic attractors in which all three species coexist and (2) by shifting or delaying the boundary crises at which the chaotic attractor loses stability and the top predators, the carnivores, disappear. We interpret this loss of the carnivores induced by the boundary crisis as a non-equilibrium manifestation of the paradox of enrichment.