Host plant protection by arboreal ants: looking for a pattern in locally induced responses

Background: Among arboreal ants, both territorially dominant species and plant-ants (e.g. species associated with myrmecophytes or plants housing them in hollow structures) protect their host trees against defoliators. Yet, locally induced responses, or the recruitment of nest-mates when a worker discovers a wound on its host-tree, were only noted in plant-ants. We wondered whether this might be due to the examination of the phenomenon being restricted to only six plant-ant species belonging to four genera. Based on the ant genus Azteca, a Neotropical group of arboreal species, we compared five species. The territorially dominant, carton-nester A. chartifex, three plant-ant species [A. alfari and A. ovaticeps associated with myrmecophitic Cecropia (Cecropiaceae), and A. bequaerti associated with Tococa guianensis (Melastomataceae)], and A. schimperi thought to be a temporary social parasite of true Cecropia ants. Methods: We artificially inflicted wounds to the foliage of the host tree of the different ant species. We then compared the number of workers on wounded versus control leaves. Results: We noted a locally induced response in the three plant-ant species as well as in the territorially dominant species, but very slightly so in A. schimperi.