The Effects of Competitive Asymmetry on the Rate of Competitive Displacement: How Robust is Hubbellʹs Community Drift Model?

It is intuitively clear that the average time required for competitive exclusion increases as the competitive abilities of species become closer to equal. To emphasize the importance of this point for understanding diversity patterns, Hubbell and his colleagues modeled tropical rainforest dynamics under the extreme assumption of competitive equivalency. In this study, we aim to extend Hubbellʹs community drift model to the cases of unequal competitive abilities. We find that a slight variation upon the assumption of equality of species could cause a considerable decline in the persistence time of species. Since species cannot be ecologically identical in any real ecosystems, we conclude that the community drift hypothesis is, at best, rather restricted in the domain of applicability.