Can endogenous fluctuations persist in high-diversity ecosystems?

Abstract

When can complex ecological interactions drive an entire ecosystem into a persistent nonequilibrium state, where species abundances keep fluctuating without going to extinction? We show that high-diversity spatially-extended systems, in which conditions vary somewhat between spatial locations, can exhibit chaotic dynamics which persist for extremely long times. We develop a theoretical framework, based on dynamical mean-field theory, to quantify the conditions under which these fluctuating states exist, and predict their properties. We uncover parallels with the persistence of externally-perturbed ecosystems, such as the role of perturbation strength, synchrony and correlation time. But uniquely to endogenous fluctuations, these properties arise from the species dynamics themselves, creating feedback loops between perturbation and response. A key result is that the fluctuation amplitude and species diversity are tightly linked, in particular fluctuations enable dramatically more species to coexist than at equilibrium in the very same system. Our findings highlight crucial differences between well-mixed and spatially-extended systems, with implications for experiments and their ability to reproduce natural dynamics. They shed light on the maintenance of biodiversity, and the strength and synchrony of fluctuations observed in natural systems.

Dynamical persistence in high-diversity resource-consumer communities

“…Still, the remaining species might continue to fluctuate for extremely long times without inducing extinctions. This has been shown recently for many-species meta-communities with random Lotka-Volterra interactions in [ 22 , 23 ]. An example simulation, provided as a proof-of-principle, is given in S1 Text (Appendix G).…”

“…In Sec. Species abundance distribution and diversity we consider this question directly in a high-dimensional setting, in light of works on high-dimensional chaos in well-mixed communities [ 6 , 14 ] and meta-communities [ 22 , 23 ]. Finally, the Conclusions section concludes with a discussion, focusing on predictions for experiments and natural communities.…”

Chaos may lurk under a cloak of neutrality

“…the chaotic bloom-bust cycles actually emerge in a large class of ecological models. They further point out that spatiotemporal chaos may also emerge in communities with selective differences and in the presence of uncorrelated interspecies interactions or moderate niche-like interactions, as shown in parallel work (20).…”

Intrinsic ecological dynamics drive biodiversity turnover in model metacommunities

“…Empirical observation of many of the emergent phenomena associated with ecological structural instability provides strong indirect evidence for the prevalence of structural instability in nature 23,31 . Our understanding of the impact of structurally unstable diversity regulation on temporal community-level properties, however, remains incomplete 32 .…”

“…Empirical observation of many of the emergent phenomena associated with ecological structural instability provides strong indirect evidence for the prevalence of structural instability in nature 23,31 . Our understanding of the impact of structurally unstable diversity regulation on temporal community-level properties, however, remains incomplete 32 . In our metacommunity model, local community dynamics and therefore local limits on species richness depend on a combination of abiotic and biotic filtering (non-uniform responses of species to local conditions) [33][34][35] and immigration from adjacent patches, generating so called mass effects in the local community [36][37][38] .…”