Do non-myrmocophilic epiphytes influence community structure of arboreal ants?

In a one-year-survey in Panama we examined the influence of a tree crown's epiphyte assemblage on its ant fauna. Ants were collected with various types of insect traps in 25 crowns of Annona glabra trees. The study trees were assigned to three different categories according to their epiphyte load, and to an epiphyte-free control group. We collected 22,335 specimens of 91 morphospecies, 32 genera and six subfamilies. By far the most abundant species was Solenopsis zeteki, a minute Myrmicinae, which was found in each of the 25 study trees. Many other species were also rather common and widely distributed throughout the study area. Only six species were singletons. Measures of alpha- and beta-diversity, species abundance and species composition were not affected by the epiphyte load of a tree. We also made direct in situ observations of ants on 34 additional Annona glabra trees with and without epiphytes. Workers were attracted with tuna and sugar baits, and interspecific interactions and nesting sites were recorded. in total, 40 species of ants were found, all of which had also been collected in the traps. Almost half of the colonies (48%) used dead wood as nesting substrate, while 29% nested in epiphytes. Consistent with the results of the trap survey, the epiphyte load of the study trees had no influence on ant species richness and composition, but a significant correlation between ant abundance and epiphyte load was detectable. In both data sets, the lack of associations between ant species indicated that the ant assemblages were not structured in a mosaic-like fashion. We conclude that epiphytes do hardly influence the composition of ant assemblages in the studied tree crowns, probably because arboreal ants are highly opportunistic with respect to their host plants.