The Ideal Free Strategy with Weak Allee Effect

This paper examines the interplay between optimal movement strategies and the weak Allee effect within the context of two competing species in a spatially heterogenous environment. When both species have the same populations dynamics, previous studies identified an ‘ideal free’ strategy which is able to exclude any other competitor playing a ‘non-ideal free’ strategy. We find that if the ideal free disperser is subject to a weak Allee effect, a competing species utilizing very weak or very strong advection will still be excluded despite having superior population dynamics. However, for intermediate advection rates, such a competitor can invade the ideal free disperser and even drive it to extinction. Not only do these results enhance ecological understanding of competing species, but they provide insight into the theory of reaction–advection–diffusion models when the usual linearization techniques offer no information.