Plant species specificity of ant-plant mutualistic interactions: Differential predation of termites by Camponotus crassus on five species of extrafloral nectaries plants

There is increasing evidence that the outcomes of mutualistic interactions between ants and plants bearing extrafloral nectaries (EFNs) are context-dependent. In particular, the total number, density, and size of EFNs, as well as the abundance and identity of ants attending host plants, are considered as key factors determining the nature and strength of ant-EFN-bearing plant interaction. Although many previous studies have investigated context-dependency in ant-plant protection mutualisms mediated by EFNs, few have tested whether the protective behavior of ants varies among sympatric plant species. In this study, we performed a field experiment to investigate the predatory behavior of a dominant ant species (Camponotus crassus, Formicinae) among five EFN-bearing plant species growing in the Brazilian savanna. In particular, we studied the variation in the ant abundance, termite predation, and time spent to find termites of C. crassus among the plant species, and further analyzed whether this variation could be related to the extrafloral nectar volume and sugar concentration of each plant species. We found that abundance and termite predation of C. crassus markedly varied among plant species. Specifically, C. crassus ants were significantly more abundant, active, and protective in Qualea multiflora, the plant species that produced significantly higher volumes and sugar concentrations of nectar. Overall, our results suggest that variation in extrafloral nectar volume and sugar concentration can result in plant species specificity of defensive behavior of a dominant foliage-dwelling ant in the Brazilian savanna. Abstract in Portuguese is available with online material.

Automated summary

The outcomes of mutualistic interactions between ants and plants bearing extrafloral nectaries (EFNs) are context-dependent, influenced by factors such as the number, density, and size of EFNs, as well as the identity and abundance of attending ants. A field experiment in the Brazilian savanna found that the predatory behavior of Camponotus crassus ants varied among five EFN-bearing plant species, with significantly greater abundance and activity in the plant species producing higher volumes and sugar concentrations of extrafloral nectar.