Experimental demonstration of species coexistence enabled by dispersal limitation

Abstract

Summary 1 Dispersal limitation is widely invoked to explain species coexistence and cooperation in the face of competition and cheating. However, empirical evidence from natural ecosystems for the stabilizing effect of space is sparse. 2 We use a Neotropical ant–plant and its ant symbionts to show how mutual dispersal limitation brings about the stable persistence of coexistence and mutualism. 3 We demonstrate that two ant genera exhibit hierarchies in competitive ability, fecundity and dispersal ability, which suggests that a competition–colonization trade-off could be producing coexistence. However, we also show that this trade-off is not a sufficient explanation for coexistence. 4 Instead, we provide evidence that a dispersal–fecundity trade-off stabilizes the system by making each genus more dispersal-limited in a different portion of the environment. In this way, dispersal limitation can be seen as a form of environmental niche partitioning. 5 We also find that regeneration niche partitioning and a competition–colonization trade-off may help to bring about local mixing. 6 This study shows that care needs to be taken in identifying the critical mechanisms producing coexistence. Trade-offs between different stages of colonization may be more important for explaining coexistence than any trade-offs between competitive ability and colonization rate.