ON COMPETITION-MEDIATED COEXISTENCE

Two competing species, denoted B and C, currently inhabit a common hab itat patch. Left alone. B can be expected to exclude C from the patch over time. An exotic species A is introduced into the patch. A compete s with both B and C. Absent B, A can also be expected to exclude C fro m the patch over time, whereas absent C, A and B can be expected to co exist. Whether or not the introduction of A into the habitat patch mak es for the long-term coexistence of all three species is examined in t his article via reaction-diffusion models. It is shown that such an ou tcome depends on the precise qualitative nature of the pair wise compe titive interactions. In particular, long-term coexistence of all three species cannot be expected in the case of Lotka-Volterra models but c an be expected for suitable modifications of such models.