Variation in community structure of gall-inducing insects associated with a tropical plant supports the hypothesis of competition in stressful habitats

Environmental factors act as drivers of species coexistence or competition. Mesic environments favor the action of parasites and predators on gall communities, while the factors that determine the structure of gall communities in xeric environments remain unknown. We evaluated the structure of gall communities along an environmental gradient defined by intrinsic plant characteristics, soil fertility and aridity, and investigated the role of competition as a structuring force of gall communities in xeric environments. We created null models to compare observed and simulated patterns of co-occurrence of galls and used the C-score index to assess community aggregation or segregation. We used the NES C-score (standardized C-score) to compare patterns of co-occurrence with parameters of environmental quality. Xeric environments had poorer and more arid soils and more-sclerophyllous plants than mesic environments, which was reflected in the distribution patterns of gall communities. Values of...