Patterns of species interaction strength in assembled theoretical competition communities

Strength of interactions between species may be an important tool in our ef fort to understand community structure. Recent theoretical and empirical fi ndings suggest that despite the presence of some strong interactions, weak interactions prevail in communities. Here, we examine how mean interaction strengths change as theoretical competition communities assemble and what t he distribution of interaction coefficients is in the communities that are formed during the assembly process. Our results show that the mean competit ion strengths fall as assembly progresses and that most interactions in the communities formed are weak. Communities that are invulnerable to further invasions are these where interspecific interactions are weaker than the av erage interaction strength between species in the pool. Ii these results ca n be generalized to more than one trophic level, implications for managemen t and conservation of natural communities are substantial.