Coexistence of species via a trade-off between colonization and competitive abilities: New theoretical insights

The competition-colonization trade-off model is often used to explain the coexistence of species and to adress the consequences of habitat destruction on biodiversity loss. Yet its applicability has been severely criticized, mainly because earlier formulations of the model relied on ecologically unrealistic assumptions: a strict competitive hierarchy (i.e. an infinite trade-off), and no preemptive effects. We extended the classical competition-colonization trade-off model in order to relax these two assumptions. We found that species coexistence is quite robust to the introduction of moderate trade-off intensities and preemptive effects. Surprisingly, preemption does not impede coexistence as one could presume from previous studies, but can actually increase the likelihood of species coexistence. Premption is predicted to favour coexistence when: (i) species are not strongly limited in their colonization ability; and (ii) the competitive trade-off is not infinitely intense. We explain our results by the existence of a « limit to dissimilarity » between species, in addition to the classical limit to similarity. Finally, we discuss our results with emphasis on their implications for community assembly and biodiversity accumulation.