1. Herbivorous insects can be classified into several trophic guilds with different levels of specialisation on their host plants, which may influence the topological structure of their trophic networks. The present study tested the hypothesis that the structure of plant-herbivore networks differs between guilds of galling, sucking, and chewing insects.2. Six areas of Neotropical savannas were studied in two localities in the North of the state of Minas Gerais, Brazil. In each area, interactions between plant and insect species were used to build networks for different guilds.3. In total, 18 plant-herbivore networks were built, comprising 317 insect morphospecies, 50 plant species, and 489 distinct interactions. The networks were characterised using species richness and different network topological measures (connectance, modularity, nestedness, and specialisation).4. The results obtained showed no difference in species richness, network size, and connectance between distinct insect herbivore guilds. However, it was found that modularity was higher for exophagous than galling insect networks and nestedness was higher for chewers than for other guilds. On the other hand, galling insect networks showed higher specialisation than exophagous insect networks, and sucking insect networks were more specialised than chewing insect networks.5. The findings of the present study indicate that, although species richness did not differ between insect guilds of herbivores in Neotropical savannas, the topological structure of networks is sensitive to biological and ecological differences between these herbivore groups. The present study stands out as the first to systematically compare the network structure of different herbivore guilds in Neotropical savannas.

Gall-forming insects are sophisticated sedentary herbivores that present high level of specificity with host plant, but their performance can be affected by biotic and abiotic factors. In this study we have tested two predictions: a) plants that have a greater number of conspecific neighbors have greater richness and abundance of gall-forming insects, and b) interspecific competition is a force capable of shaping the organization of gall-forming insect communities in super-host plants. We used the Copaifera oblongifolia (Fabaceae)/galling insects' system to test these predictions. Fieldwork was carried out in areas of Cerrado (Brazilian Savanna) in northern Minas Gerais, Brazil. To test the first hypothesis, we evaluated with generalized linear mixed models, the effects of the number of conspecific neighbors on the richness and abundance of galls associated with 67 C. oblongifolia individual plants belonging to two populations. To test the second hypothesis, we used null models to evaluate whether a plant of C. oblongifolia colonized by a species of gall is preferred or avoided by another species of gall. A total of 2901 gall-forming insects belonging to 15 species were collected from the host plant C. oblongifolia. We observed negative relationships between the number of conspecific neighbors and the abundance and richness of gall-forming insects associated C. oblongifolia. Thus, our data did not support the resource concentration hypothesis. Instead, we used the resource dilution theory to explain the negative relation between resource concentration and frequency of attack by galling insects. Our results also showed that the co-occurrence pattern of gall-forming insects in the host plant did not differ from those expected by chance. Therefore, the structure of the gall-forming insect community associated to single C. oblongifolia plants cannot be attributed to deterministic factors such as interspecific competition.

Caatinga is a very important and neglected dry tropical forest biome of Brazil. Recent evidence indicates that anthropogenic threats to Caatinga have grown in recent years, and there are still gaps in the knowledge of how these effects alter biodiversity. In the present study, we evaluated the effects of vegetation structure and edge proximity on the distribution of bioindicator insects (galling insects and ants) in an arboreal Caatinga area under the influence of a monoculture in Brazil. We recorded a total of 10 species and 2,131 specimens of ants and 11 species and 29 individuals of galling insects. Species richness, abundance, and composition of galling insects and ants did not differ between edge and interior plots of the forest. Ant diversity was also not affected by the structural parameters of vegetation (plant abundance, vegetation cover, and vegetation height). On the other hand, the plant abundance positively influenced the richness and the abundance of galling insects in the plots. Our findings suggest that the distribution of ants and galling insects in Caatinga forest edge and interior environments did not differs likely due the opening of the canopy gives the arboreal Caatinga relatively homogeneous climatic characteristics throughout the forest. Already the structure of vegetation positively influences galling insects due to the high degree of dependence that endophagous life-form generates on these insects. Our results show that despite similar responses to the edge effect, ants and galling insects respond differently to vegetation structure, indicating that the structuring of these insect communities is guild-dependent.

Plant-insect interactions can differ between endophagous and exophagous insect guilds, and this can influence the response patterns of these guilds to anthropogenic changes in natural habitats. We compared the species richness, abundance, and species-level specialization of plant-herbivore assemblages composed of distinct insect guilds in Neotropical savannas. Assemblages of chewing insects were the richest in species, and the gallers were the most abundant. Galling species were more specialized than other guilds, and sucking insects were more specialized than chewers.Our results show that insect guilds are similarly influenced by disturbance, which decreased species richness and increased specialization of insect species.