# Alternative steady states in random ecological networks

## TL;DR

This paper investigates the number of stable, uninvadable states in large, random ecological networks, revealing exponential growth with species number under certain conditions and linking it to network clique structures.

## Contribution

It introduces a model connecting stable states in ecological networks to maximum cliques in near-complete graphs, especially in the weak competition and high variance limit.

## Key findings

- Number of stable states grows exponentially with species in symmetric networks.
- Asymmetry in competition reduces the number of stable states to a constant order.
- Numerical simulations support the applicability to continuous competition distributions.

## Abstract

In many natural situations one observes a local system with many competing species which is coupled by weak immigration to a regional species pool. The dynamics of such a system is dominated by its stable and uninvadable (SU) states. When the competition matrix is random, the number of SUs depends on the average value of its entries and the variance. Here we consider the problem in the limit of weak competition and large variance. Using a yes/no interaction model, we show that the number of SUs corresponds to the number of maximum cliques in a network close to its fully connected limit. The number of SUs grows exponentially with the number of species in this limit, unless the network is completely asymmetric. In the asymmetric limit the number of SUs is ${\cal O} (1)$. Numerical simulations suggest that these results are valid for models with continuous distribution of competition terms.