Synchrony and Stability in Trophic Metacommunities: When Top Predators Navigate in a Heterogeneous World

Abstract

Ecosystem stability strongly depends on spatial aspects since localized perturbations spread across an entire region through species dispersal. Assessing the synchrony of the response of connected populations is fundamental to understand stability at different scales because if populations fluctuate asynchronously, the risk of their simultaneous extinction is low, thus reducing the species' regional extinction risk. Here, we consider a metacommunity model consisting of two food chains connected by dispersal and we review the various mechanisms governing the transmission of small perturbations affecting populations in the vicinity of equilibrium. First, we describe how perturbations propagate vertically (i.e., within food chains through trophic interactions) and horizontally (i.e., between food chains through dispersal) in metacommunities. Then, we discuss the mechanisms susceptible to alter synchrony patterns such as density-depend dispersal or spatial heterogeneity. Density-dependent dispersal, which is the influence of prey or predator abundance on dispersal, has a major impact because the species with the highest coefficient of variation of biomass governs the dispersal rate of the dispersing species and determines the synchrony of its populations, thus bypassing the classic vertical transmission of perturbations. Spatial heterogeneity, which is a disparity between patches of the attack rate of predators on prey in our model, alters the vertical transmission of perturbations in each patch, thus making synchrony dependent on which patch is perturbed. Finally, by combining our understanding of the impact of each of these mechanisms on synchrony, we are able to full explain the response of realistic metacommunities such as the model developed by Rooney et al. (2006). By disentangling the main mechanisms governing synchrony, our metacommunity model provides a broad insight into the consequences of spacial aspects on food web stability.

Ecosystem connectivity and configuration can mediate instability at a distance in metaecosystems

“…Here instability is any form of dynamics that threatens the persistence of a species locally or across the metacommunity. Connectivity via the spatial flows of nutrients, resources and consumers can carry or even amplify the destabilising effects of point sources of disturbance and perturbation over large distances (7,12).…”

“…For example, changes in the rates of movement of consumers may synchronise consumer dynamics driving instability (13), leading to greater metacommunity instability, as measured by increases in the variance in population dynamics within and among local communities (12).…”

“…Here instability is any form of dynamics that threatens the persistence of a species locally or across the metacommunity. Connectivity via the spatial flows of nutrients, resources and consumers can carry or even amplify the destabilising effects of point sources of disturbance and perturbation over large distances (7, 12). For example, changes in the rates of movement of consumers may synchronise consumer dynamics driving instability (13), leading to greater metacommunity instability, as measured by increases in the variance in population dynamics within and among local communities (12).…”

Ecosystem connectivity and configuration can mediate instability at a distance in metaecosystems

“…Altered patterns and rates of ecosystem connectivity can cause instability both locally and over large spatial extents at the metaecosystem level. Connectivity via the spatial flows of nutrients, resources and consumers can carry or even amplify the destabilising effects of point sources of disturbance and perturbation over large distances (McCann et al, 2021;Quévreux & Loreau, 2022).…”

“…Altered patterns and rates of ecosystem connectivity can cause instability both locally and over large spatial extents at the metaecosystem level. Connectivity via the spatial flows of nutrients, resources and consumers can carry or even amplify the destabilising effects of point sources of disturbance and perturbation over large distances (McCann et al., 2021; Quévreux & Loreau, 2022). For example, changes in the rates of movement of consumers may synchronise consumer dynamics driving instability (Gouhier et al., 2010), leading to greater metacommunity instability, as measured by increases in the variance in population dynamics within and among local communities (Quévreux & Loreau, 2022).…”