Ecological engineering by a native leaf-cutting ant increases the performance of exotic plant species

FARJI-BRENER, ALEJANDRO GUSTAVO; LESCANO, N.; GHERMANDI, L

OECOLOGIA

SPRINGER

Año: 2010 vol. 163 p. 163 - 169

0029-8549

Numerous mechanisms are proposed to explain why exotic plants successfully invade natural communities. However, the positive effects of native engineers on exotic plant species have received less consideration. We tested whether the nutrient-rich soil patches created by a native ecological engineer (refuse dumps from the leaf-cutting ant Acromyrmex lobicornis) increase the performance of exotic more than native plants. In a greenhouse experiment, individuals from several native and exotic species were planted in pots with refuse dumps (RD) and non-nest soils (NNS). Total plant biomass and foliar nutrient content were measured at the end of the experiment. We also estimated the cover of exotic and native plant species in external RD from 54 field ant nests and adjacent areas. Greenhouse plants showed more biomass and foliar nutrient content in RD than in NNS pots. Nevertheless, differences in the final mean biomass among RD and NNS plants were especially greater in exotics. Accordingly, the cover of exotic plants was relatively higher in field RD than in adjacent, non-nest soils. Our results demonstrated that plants can benefit from the enhanced nutrient content of ant RD, and that A. lobicornis acts as an ecosystem engineer creating a substrate that especially increases the performance of exotics. This supports the fluctuating resource hypotheses as a mechanism to promote biological invasions, illustrating how this hypothesis may operate in nature. Since ant nests and exotic plants are more common in disturbed than pristine environments, the role of ant nests in promoting biological invasions might be of particular interest. Proposals including engineer species to restore disturbed habitats should be planned with caution because of their potential role in promoting invasions.