Herbivory by a leaf-cutter ant, Acromyrmex lobicornis, as a possible control of nonnative pinaceae invasion in Patagonia, Argentina

DIMARCO, ROMINA D.; NASSINI, DANIELA; FARJI-BRENER, ALEJANDRO G.; CORLEY, JUAN C.; NUÑEZ, MARTIN A.

Liverpool

Conferencia; British Ecological Society Annual Meeting 2016; 2016

The British Ecological Society

Insect herbivory is a strong regulator of plant populations. In South America the problem of pinaceae invasions is a growing problem, and it has been proposed that herbivory could help control it. Leaf-cutter ants herbivory is considered a problem for the establishment of pinaceae plantations. There are 96.500 ha of pinaceae plantations in Patagonia and pinaceae frequently invade surrounding areas. These areas are sometimes occupied by colonies of the leaf-cutter ant Acromyrmex lobicornis and it is possible that this ant could control pinaceae in early stages of their invasion. Here we evaluate the foraging preference of A. lobicornis ants for pinaceae seedlings (≤ 1 year) of the most widely planted conifers in the region: Pinus ponderosa, Pinus contorta and Pseudotsuga menziesii and also for the most important native conifer, Austrocedrus chilensis. We also studied if foraging preference is related to differences in chemical and mechanical defenses. We performed a cafeteria experiment where we chose ant nests that were similar in size and foraging activity. We selected two principal trails from each nest and we planted A. chilensis seedlings (control) paired with seedlings of two different pinaceae per trail (240 seedlings total). Seedlings were planted at two distances from the entrance of the nest and also two distances from the trail to evaluate the effect of distance. To evaluate the foraging preference on the conifers, we registered the number of needles and branches removed, the height of the seedling, and the percentage of each seedling consumed. We found that ants in less than two weeks consumed almost all of the seedlings offered and that they prefer the nonantives, especially P. contorta and P. ponderosa. These results suggest that A. lobicornis could contribute to the control of pinaceae invasions in early stages, which is an important environmental problem in the continent.