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

Abstract

Fragmentation of the habitat is a major threat to global biodiversity (Kruess & Tscharntke, 1994; Foley et al., 2005). Habitat fragmentation due to anthropogenic activity results in landscapes composed of a mosaic of remnant habitats surrounded by a more or less hostile agricultural or pasture land for cattle, called the matrix. The Atlantic forest, once the largest forest in America, is an ecosystem severely affected by habitat fragmentation. Most of the remaining Atlantic forest exists as small fragments (<100 ha; Ranta et al., 1998), that are composed of second-growth forests in early to intermediate stages of succession (Metzger et al., 2009), and the few large fragments are located in steep terrain that made human occupation difficult (Silva et al., 2007). Most of the original forest is fragmented and 80% of the fragments are <50 ha, and together with intermediate secondary forests, correspond to approximately 32-40% of what remains (Ribeiro et al., 2009).

Parasitoid phorid flies of leaf‐cutting ants are negatively affected by loss of forest cover

“…The results presented in this study indicate that parasitoid phorids of the leaf‐cutting ant A. niger are affected by forest fragmentation in the Atlantic Forest. These results corroborate previous findings of the negative effect of fragmentation upon phorid parasitoids of leaf‐cutting ants in the genera Atta (Rao, ; Almeida et al., ) and Acromyrmex (Elizalde & Queiroz, ).…”

“…The nests are difficult to locate because of the underground chambers and long galleries with very discrete entrances (simple openings in the soil). Workers can be seen foraging on distinct trails, carrying leaves to feed the symbiotic fungal culture they tend within the nest (Elizalde & Queiroz, ).…”

“…2 m of the main foraging trails (Elizalde & Folgarait, ). Sampling was done in the daytime, between 10:00 and 16:00 hours, during periods when the ants were found actively foraging and, therefore, when the parasitoids would be the most active (Orr, ; Bragança et al., ; Elizalde & Queiroz, ). After collection, parasitoids were preserved in alcohol and later identified in the laboratory using a 90× dissecting microscope and with the available identification keys (Brown, ; Disney et al., , , ; Brown et al., ).…”

“…Additionally, the species of phorid parasitoids that attack one genus of leaf‐cutting ants do not attack other genera (Elizalde & Folgarait, ); therefore, our understanding of the phorid‐ Atta system cannot be extrapolated to the phorid‐ Acromyrmex system and vice versa. Evidence suggests that these parasitoids may be more negatively affected by habitat fragmentation than the ants (Almeida et al., ; Elizalde & Queiroz, ). Given the strong specialization in this system, it is very likely that any effects that fragmentation has upon phorid parasitoids could end up indirectly affecting the ants and thus the equilibrium of the entire forest community (Almeida et al., ).…”

“…The leaf‐cutting ant Acromyrmex niger Smith is highly abundant in Brazil and is considered a very harmful species for crop plants (Gonçalves, ; Elizalde & Queiroz, ). Evaluating the interactions between A. niger and parasitoid phorids is especially relevant for the development of management techniques for conservation biological control (Barbosa, ).…”