Can the nutrient-rich soil patches created by leaf-cutting ants favor plant compensation for foliar damage? A test of the compensatory continuum hypothesis
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Compensation, the degree of plant recovery after herbivory, is influenced by nutrient availability. The compensatory continuum hypothesis (CCH) predicts that the more abundant the resources in an environment, the greater the potential for compensation. Nutrient-rich patches generated by leaf-cutting ants near their nests could modify plants’ responses to damage. We performed a greenhouse and a field experiment to evaluate the effects of refuse dumps (RDs) created by Acromyrmex lobicornis on plant compensation for foliar herbivory in roadside areas of the Patagonian steppe. We expected higher tolerance in plants growing in RDs than in adjacent non-nest soils (NNSs). We also assessed whether compensation differed between native and exotic species common in the area. We expected higher compensation in exotic than native plants since they perform better in RDs. Native and exotic plants fully compensated for simulated herbivory resembling natural levels. In the greenhouse, clipped plants achieved similar biomass as control plants and in the field reproductive output was similar between treatments. However, compensation was not higher in RDs than NNSs or in exotic than native plants as expected. Both native and exotic plants in roadside areas may have traits associated with disturbance which allow them to tolerate natural occurring herbivory without compromising their performance. Our study, the first one to test the CCH on RDs, shows that enhanced levels of resources do not always determine higher tolerance to herbivory.
KeywordsAcromyrmex lobicornis Disturbance Herbivory Patagonian steppe Tolerance
We thank R. Dirzo and E. Gianoli for their critical reading and comments on an earlier draft of this manuscript. We are also grateful for the contributions of two anonymous reviewers. N. Lescano, S. González, C. Ezcurra, J. Franzese, C. Ziperovich, and L. Ghermandi helped at several stages of this study. GP was supported by a postdoctoral fellowship from CONICET (Consejo Nacional de Investigaciones Científicas y Técnicas) and financial support was partially supplied by Agencia Nacional de Promoción Científica y Tecnológica of Argentina (lately through PICT 2008-0352).
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