Phylogenetic community ecology needs to take positive interactions into account: Insights from colourful butterflies

Phylogenetic community ecology uses phylogenetic relationships among species to infer the dominant processes that shape community ecological structure. This field has particularly focused on habitat filtering and competition, the latter driving divergence and competitive exclusion. However, the effects of positive interactions among species of the same guild have rarely been considered in either empirical studies or theoretical models. We have recently documented a pervasive influence of mutualism in driving adaptive convergence in ecological niche. Müllerian mimicry in butterflies is one of the best-studied examples of mutualism, where unpalatable species converge in wing pattern locally to advertise their toxicity to predators. We showed that species that share similar wing patterns are more similar in their ecology than expected given the phylogeny and co-exist at a fine spatial scale, thereby maximizing the warning signal to local predators. Evidence for competition was detected only among species with distinct wing patterns, implying that mutualistic interactions outweigh the effects of competition. Positive interactions among potential competitors are common among plants and animals. We argue that such forces should be considered in the field of phylogenetic community ecology, along-side neutral processes, habitat filtering and competition.