Persistence in randomly switched Lotka-Volterra food chains

TL;DR

This paper studies the long-term behavior of randomly switching Lotka-Volterra food chains, showing conditions for species persistence or extinction and analyzing the model's sensitivity to parameters.

Contribution

It establishes a link between the existence of a positive equilibrium of the average vector field and species persistence under random switching.

Findings

Positive equilibrium implies species persistence.

Failure of equilibrium leads to extinction or critical cases.

Exponential convergence to invariant measures.

Abstract

We consider a dynamical system obtained by the random switching between $N$ Lotka-Volterra food chains. Our key assumption will be that at least two vector fields only differ on the resources allocated to the growth rate of the first species. We will show that the existence of a positive equilibrium of the average vector field is equivalent to the persistence of all species. Under this condition, the semi-group converges exponentially quickly to a unique invariant probability measure on the positive orthant. If this condition fails to hold, we have two possibilities. The first possibility is the extinction case, in which a group of species becomes extinct exponentially quickly while the distribution of the remaining species converges weakly to another invariant probability measure. The second possibility is the critical case, in which there is a weaker form of persistence of some species, whilst some of the remaining become extinct exponentially quickly. We will also analyse the sensitivity of this model to the parameters.