Structure of dung beetle assemblages (Coleoptera: Scarabaeidae: Scarabaeinae) in native forest and exotic pastures in the Southwest of the Brazilian Amazon

The implementation of exotic pastures is responsible for significant deforestation in the Amazon rainforest. The pasturelands in the Amazon are created through both legal and illegal means, and are responsible for major biodiversity loss. In this study, we evaluated the effect of an anthropogenic habitat type (i.e., exotic pasture) on native dung beetle assemblages (Coleoptera: Scarabaeidae: Scarabaeinae) – an excellent bioindicator group for measuring biodiversity-loss. We analyzed dung beetle diversity and assemblage structure in a large and well-conserved forest fragment and in an exotic pasture (Urochloa brizantha cv. Marandu; Poaceae) that is used for cattle-ranching activities, both located in the Southwestern Brazilian Amazon. A total of 569 individuals belonging to nine genera and 31 species of dung beetles were collected. From the sampled species, 13 were collected in both habitats, 16 species were exclusive to the native forest, and only two were found exclusively in the exotic pasture. Species richness as a whole and specifically of paracoprid dung beetles was higher in the forest fragment. Our findings also revealed a distinct assemblage structure between native forest and exotic pasture. In conclusion, our results provide evidence that the dung beetle assemblage in exotic pasture is a subset of the assemblage present in native forest, with a poor richness of species, indicating that dung beetles are drastically affected by the opening of new areas for implementation and expansion of pasturelands in the Amazon.