Predators and parasitoids sharing a leaf-cutting ant prey (Acromyrmex lobicornis): Preliminary results of complex interactions

ELIZALDE, LUCIANA; MEIER, DIEGO

Simposio; Simposio de Mirmecologia; 2013

Predators and parasitoids that share the same prey can interact negatively trough intraguild predation or competition for the resource. But they can also interact positively, by increasing prey availability for the other. Leaf-cutting ants are preyed upon by various vertebrates and invertebrates, but one of the most important are armadillo mammals. These ants are also attacked by a group of phorid parasitoids, which form a guild in the sense that they only use leaf-cutting ants as hosts to oviposit in. Armadillos, phorid parasitoids and leaf-cutting ants overlap in much of their distribution range and constitute a good study system to research predator?parasitoid?prey trophic interactions. Here, we present preliminary results evaluating whether these predators and parasitoids interact through their common prey, the leaf-cutting ant Acromyrmex lobicornis in Patagonia (Argentina). Since the system is unknown, we also describe basic aspects of these interactions as a necessary first step. Along transects we 1) counted the number of nests with signs of attack by the armadillo Chaetophractus villosus, 2) collected their feces to later identify ants in them, and 3) collected ants to rear phorids from them in some of these nests. A 48% of the nests suffered armadillo attack (N = 65 nests), and the feces analysis allowed to determine that these mammals feed on ants with high frequency (67% of the feces had A. lobicornis), and that ants represented the dominant insect food resource (although armadillos also fed on vegetables). We found that 80% of nests were parasitized by the phorid species Myrmosicarius catharinensis (N = 10 nests). In nests with phorids, 3 ± 2.1% (mean ± SD) forager ants were parasitized. This mean parasitism is similar to values found in other localities by this phorid species. However, we found no significant differences in the percentage of ants parasitized by phorids between nests with and without armadillo attacks (U = 10, P = 0.57, N = 8 nests). These preliminary results suggest that predators and parasitoids are not interacting through their shared prey. However, we are conducting field experiments to determine the potential for interactions mediated by their common prey in this predator-parasitoid system. These results may be important for integrated biological control of these ants when they have become pests, and also to avoid them to become pests. (Fundación Bunge y Born, Argentina)