Synchrony and Perturbation Transmission in Trophic Metacommunities

Abstract

In a world where natural habitats are ever more fragmented, the dynamics of metacommunities are essential to properly understand species responses to perturbations. If species' populations fluctuate asynchronously, the risk of their simultaneous extinction is low, thus reducing the species' regional extinction risk. However, identifying synchronising or desynchronising mechanisms in systems containing several species and when perturbations affect multiple species is challenging. We propose a metacommunity model consisting of two food chains connected by dispersal to study the transmission of small perturbations affecting populations in the vicinity of an equilibrium. In spite of the complex responses produced by such a system, two elements enable us to understand the key processes that rule the synchrony between populations: (1) knowing which species have the strongest response to perturbations and (2) the relative importance of dispersal processes compared with local dynamics for each species. We show that perturbing a species in one patch can lead to asynchrony between patches if the perturbed species is not the most affected by dispersal. The synchrony patterns of rare species are the most sensitive to the relative strength of dispersal to demographic processes, thus making biomass distribution critical to understand the response of trophic metacommunities to perturbations. We further partition the effect of each perturbation on species synchrony when perturbations affect multiple trophic levels. Our approach allows disentangling and predicting the responses of simple trophic metacommunities to perturbations, thus providing a theoretical foundation for future studies considering more complex spatial ecological systems.

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“…Variances w i are the diagonal elements of the variance-covariance matrix C* of the system obtained by solving the Lyapunov equation (Arnold, 1974;Arnoldi et al, 2016;Shanafelt & Loreau, 2018;Wang et al, 2015: J is the Jacobian matrix, V E is the covariance matrix of perturbations and T describes how perturbations affect the system. (Matrices are detailed in section S1-1 in the Supporting Information and see Quévreux, Barbier, et al (2021) for a detailed description of the Lyapunov equation. )…”