Parasitoids of Acromyrmex (Hymenoptera: Formicidae) Leaf-Cutting Ants in Continuous and Fragmented Atlantic Forest

Abstract

Fragmentation of the habitat is a major threat to biodiversity in Atlantic forest. Parasitoids seem to be particularly susceptible to habitat fragmentation. This study evaluated whether habitat fragmentation affected the interactions between phorid parasitoids and their Acromyrmex leaf-cutting ant host. Host density, and parasitoid species richness, abundance and proportion of nests with phorids were compared for a fragmented landscape and a well-preserved continuous forest in the Atlantic forest in Rio de Janeiro. Five Acromyrmex species and seven species of phorid parasitoids were found, most of them attacking exclusively Acromyrmex niger (Smith). Host nest density was similar in continuous and fragmented forests, and host species density was higher in fragmented forest. Parasitoid species richness, abundance and proportion of ant nests with phorids were higher in the continuous forest. This work showed for the first time the negative effect that forest fragmentation has on parasitoid species of Acromyrmex ants, apparently due to phorid inability to reach fragments. However, even when phorid abundance was considerably reduced in forest fragments, phorids of some species were able to parasitize ants there. In addition, the quantitative interactions among Acromyrmex ants and their parasitoids in Atlantic forest are described for the first time.

Keywords

• habitat fragmentation
• Phoridae
• species richness
• host-parasitoid interactions
• Apocephalus
• Myrmosicarius