Abstract

SIMONETTI, Gastón  and  DEVOTO, Mariano. The defence of Passiflora caerulea by ants reduces the number of eggs and larvae of Agraulis vanillae, but not the damage by herbivory. Ecol. austral [online]. 2018, vol.28, n.1, pp.123-132. ISSN 1667-782X.

The system consisting of the plant Passiflora caerulea, the ants that visit its extrafloral nectaries and the larvae of the Gulf fritillary butterfly (Agraulis vanillae) that feed on the plant provides an opportunity to explore the effect of one ecological interaction on another. The objective of this work was to study the effect of the mutualism between the ants and the plant on the antagonism between the butterfly larvae and the plant. The general hypothesis tested was that ants protect the plant from the attack of the larvae "in exchange" for the nectar they receive. An ant exclusion experiment was conducted to explore whether their presence affects the presence of eggs and larvae and the damage they produce. This experiment was carried out at Parque Natural Municipal Ribera Norte (PNMRN), located in the San Isidro party, in the province of Buenos Aires, between September 2011 and March 2012. Five different ant morphotypes were recorded on P. caerulea. According to what was expected, there was a negative effect of the ants on the number of eggs and larvae of A. vanillae. However, the presence of ants did not affect the level of herbivory damage observed. In other words, the protection mutualism had a negative effect on the herbivore attacked (in this case, the butterfly), but did not seem to have the expected positive effect on the defended plant (the Passiflora). This reflects the complexity of tripartite interactions in plant-herbivore-ant systems and the multiple factors that may influence how the species involved are affected. From the point of view of the conservation of biodiversity and its functions in a threatened environment, it is remarkable to have registered the occurrence of these interactions in a small urban nature reserve such as PNMRN.

Keywords : Plant-herbivore interaction; Defence against herbivory; Urban reserve.

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