Changes in the dynamics of functional groups in communities of dung beetles in Atlantic forest fragments adjacent to transgenic maize crops

Abstract

We investigated the composition and structure of dung beetle communities (Coleoptera, Scarabaeidae, Scarabaeinae) inhabiting areas of forest fragments next to either conventional or Bt-transgenic maize crops. The purpose of the study was to examine possible impacts of transgenic plants on non-target organisms associated with mammals through their food chain. In February 2011, we collected a total of 1502 beetles belonging to 33 species in Campos Novos, Santa Catarina state (SC), Brazil. Beetles were captured using 200 pitfall traps distributed among 20 forest fragments, 10 fragments in each site type (adjacent to conventional vs. Bt crops). In the fragments adjacent to conventional maize, 805 dung beetles from 27 species were collected. In the fragments adjacent to Bt-transgenic maize, 697 dung beetles from 27 species were caught. Dung beetle community composition was affected by fragment size and environmental complexity, and by distance between fragments. However, it did not explain the differences related to the two crop types, i.e., the functional group of dwellers was significantly over-represented in the fragments surrounded by transgenic maize. Hence, the dweller species Eurysternus francinae and Eurysternus parallelus were more frequent and abundant in fragments located near the transgenic maize, while the tunneler species Onthophagustristis, Uroxys terminalis, Ontherus sulcator and the roller species Canthon lividus seminitens were more frequent and abundant in fragments surrounded by conventional maize. This observed impact of transgenic crops on functional group dynamics within dung beetle communities could potentially lead to impaired capacity for feces removal, seed dispersal, edaphic aeration, and incorporation of organic matter in the soil in these areas, as such ecosystem services are not performed by the dominant functional group (i.e., dwellers).