Fig. 4. Priority effects occur when final equilibrium population sizes are dependent on initial population sizes, even though all other parameter values (that is, environmental conditions) remain unchanged.

Such priority effects occur in the IGP module when competition between the apex predators and the mesopredators is strongest, illustrated here with two simulations that differ only in the initial abundance of the apex predator. (A) The dynamics illustrate the scenario where the apex predator’s initial population size (green, P₀ > 0.1) is sufficient to affect the extinction of the mesopredator (blue, N₀ = 0.01). (B) In contrast, the dynamics illustrate a scenario where the apex predator’s initial population size (P₀ < 0.1) is insufficient to avoid extinction due to exclusion by the mesopredator (N₀ = 0.01) (that is, a failed restoration). Parameters are as in Figs. 2 and 3 but with ω = 0.225 reflecting an IGP module in which exploitative competition is strong.