Ant habitat-use guilds response to forest-pasture shifting in the southwestern Amazon

Ant assemblages have been used as bioindicators of biodiversity response to different types of anthropogenic disturbances. However, usual diversity metrics (e.g., ant species richness and composition) sometimes seem limited in showing an overall panorama of human impacts. Thus, we checked habitat-use guilds of ants as a complementary predictable parameter, based on the ant fauna reported in thirteen forest fragments and pastures in the southwestern Brazilian Amazon. Specifically, we hypothesized that forest specialist, open-habitat specialist, and generalist ants would have distinct responses to forest-pasture shifting. We expected that forest-pasture shifting would cause a decrease in species richness of forest specialists and an increase in open-habitat specialists, while the generalists would have few changes in their richness because they can live in both habitats. As expected, the species richness of forest specialist ants decreased, and open-habitat ants increased with forest-pasture shifting, while generalists had little change. This indicates that human-induced open habitats (e.g., pastures) are essentially comprised of generalist ants and open-habitat ant specialists, which replace forest specialists. Additionally, considering the plasticity of generalist ants, they can be considered as primary elements of ant assemblages. Therefore, a future step is to quantify the limit of forest-cover clearing in human-induced land uses, which might ensure a higher species richness of forest-specialist ants than other habitat-use guilds. Implications for insect conservation: Habitat-use ant guilds (forest specialists, open-habitat specialists, and generalists) have been used as a complementary parameter on bioindication. Here, we provided a standard protocol to classify the ant fauna in these habitat-use guilds, which allows for objective, reproducible and broad use in monitoring programs that consider ant assemblages as bioindicators.