Does spatial structure facilitate coexistence of identical competitors?

In an apparent violation of Gause's principle of competitive exclusion, many metapopulation models of interspecific competition make the claim that identical species can coexist in spatially structured habitats. In these models, it is assumed that extinction and colonization parameters are always the same for both species, independent of the relative abundance of the two species in doubly occupied patches. We show that it is this simplifying assumption that gives an unfair advantage to the regionally rarer species. More realistic assumptions in these models would lead to different conclusions, which indicate that two identical species cannot coexist regionally in a network of many habitat patches.