Survival of the Scarcer

TL;DR

This paper studies how two competing species coexist and go extinct in a stochastic model, revealing that the less competitive species can survive longer due to discrete noise effects in finite populations.

Contribution

It introduces a stochastic model of two competing species and uncovers the paradoxical survival advantage of the less competitive species due to noise.

Findings

Both species eventually go extinct, but extinction times are exponentially long.

The less competitive species can survive longer than the more competitive one under certain conditions.

Discrete noise significantly influences extinction dynamics in finite populations.

Abstract

We investigate extinction dynamics in the paradigmatic model of two competing species A and B that reproduce (A-->2A, B-->2B), self-regulate by annihilation (2A-->0, 2B-->0), and compete (A+B-->A, A+B-->B). For a finite system that is in the well-mixed limit, a quasi-stationary state arises which describes coexistence of the two species. Because of discrete noise, both species eventually become extinct in time that is exponentially long in the quasi-stationary population size. For a sizable range of asymmetries in the growth and competition rates, the paradoxical situation arises in which the numerically disadvantaged species according to the deterministic rate equations survives much longer.