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.
We investigate how the vertical transmission (i.e. how perturbations propagate within a food chain) and the horizontal transmission (i.e. how perturbations propagate between food chains), respectively depending on which species are perturbed and which species disperse, control the synchrony between species' populations.
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. We use the Lyapunov equation, which links the covariance matrix of perturbations to the covariance matrix of species biomass, to compute the correlation coefficients and thus assess species' synchrony. By varying ecological and physiological parameters and dispersal rates, our model maps the general response of metacommunities to a broad range of conditions.
Results/Conclusions
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. In our model, dispersal affects rare species the most, 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 several independent perturbations are applied. This enables us to accurately identify the contribution of each species and of each perturbation to complex correlation patterns between species' populations.
Our approach allows disentangling and predicting the responses of simple trophic metacommunities to multiple perturbations, thus providing a theoretical foundation for future studies considering more complex spatial ecological systems.