Positive and negative interactions jointly determine the structure of Müllerian mimetic communities

Negative and positive ecological interactions have opposite effects on the structure of ecological communities, in particular in terms of ecological similarity among interacting species. In nature, species belonging to the same guild often interact in both negative and positive ways, yet the interplay between interactions of different kinds in intraguild community dynamics remains poorly understood. Müllerian mimetic communities are particularly suited for investigating this interplay because positive (mutualistic mimicry) and negative (competition for trophic resource and micro-habitat) interactions are relatively easy to identify. Empirical research has shown that the combination of competition and mutualistic mimicry does not necessarily drive convergence along all dimensions of the ecological niche, but the determinants of such mixed result are unknown. Here, we analyze the structure of Müllerian mimetic communities simulated with an agent-based model. We show that mutualistic mimicry favours ecological similarity on dimensions along which similarity favours fine-scale co-occurrence. Co-mimetic species use similar micro-habitats, but do not necessarily use similar resources. Heterogeneity of resources among micro-habitats is necessary for ecological similarity on resource use among co-mimetic species to occur. We therefore highlight the importance of fine-scale co-occurrence if we are to understand how positive and negative interactions structure ecological communities.