Community structure of gall-inducing insects associated with a tropical shrub: regional, local and individual patterns

The organization of gall-inducing insect communities can be affected by environmental factors and host plant traits that may operate at different spatial scales. Using Copaifera oblongifolia (Fabaceae), we evaluated the organization of their associated gall-inducing insect species in different spatial scales considering the following hypotheses: (i) the community of gall-inducing insects will be different between different populations of C. oblongifolia; (ii) plant individuals with a greater number of neighbours (host plant density) will have a greater diversity of gall-inducing insects; (iii) and more structurally complex plants will support a greater diversity of gall-inducing insects. Data were collected from the three different populations of C. oblongifolia located in abandoned pastures of three different municipalities in northern Minas Gerais, Brazil. We recorded a total of 17,843 galls belonging to 15 different gall-inducing insect species associated to 60 C. oblongifolia plants sampled in the three populations (20 individuals per population). Abundance, richness and composition of gall-inducing insect species were different between the populations, suggesting that local environmental conditions influenced the gall-inducing insect community at a regional scale. Host plant density negatively affected the richness and abundance of gall-inducing insects per plant. Our data did not corroborate the hypothesis of resource concentration, perhaps due to the effect of resource dilution. The biomass of the host plant positively influenced the abundance of gall-inducing insects per plant. However, the interaction between plant density and biomass of the plant suggests that plants with greater structural complexity are more attacked by gall-inducing insects in plots with lower number of neighbours.