The competition-colonization trade-off model is commonly used to explain how species coexist, but its validity has been criticized because the original model assumed a strict competitive hierarchy and excluded preemptive effects. This study examined how relaxing these assumptions influences coexistence.
The findings show that weakening the intensity of the trade-off reduces the likelihood of coexistence and creates a minimum colonization threshold below which coexistence cannot occur. Introducing preemption places a limit on how dissimilar species can be. Contrary to expectations from earlier studies, preemption does not necessarily hinder coexistence and may even enhance it.
Its impact depends on whether species in the regional pool are strongly constrained in their colonization ability. Overall, preemption is predicted to promote coexistence when species are not severely limited in colonization and when the competitive trade-off is not infinitely strong.
