Preemption of space can lead to intransitive coexistence of competitors

Intransitive competition has the potential to be a powerful contributor to species coexistence, but there are few proposed biological mechanisms that could create intransitivities in natural communities. Using a three‐species model of competition for space, we demonstrate a mechanism for coexistence that combines a colonization–competition tradeoff between two species with the ability of a third species to preempt space from the other competitors. The combination of differential abilities to colonize, preempt, and overtake space creates a community where no single species can exclude both of its competitors. The dynamics of this kind of community are analogous to rock‐paper‐scissors competition, and the three‐species community can persist even though not all pairs of species can coexist in isolation. In distinction to prior results, this is a mechanism of intransitivity that does not require nonhierarchical local interference competition. We present parameter estimates from a subtidal marine community illustrating how documented competitive traits can lead to preemption‐based intransitivities in natural communities, and we describe methods for an empirical test of the occurrence of this mechanism.