A canopy dominant ant affects twig-nesting ant assembly in coffee agroecosystems

One commonly studied driver of community assembly is the eff ect of dominant species on subordinate species. Dominant species may impact community assembly during competitive sorting, or recruitment. For ants, important and abundant species in the tropics, several factors may drive community assembly including competition, dispersal, priority eff ects, and environmental conditions. Although competition is a hallmark of ant ecology, few have examined the infl uence of patchily distributed dominant ants on other ant species and diversity, especially at the recruitment stage. Here, I consider the impacts of a canopy dominant ant species, Azteca instabilis , and changes in vegetation on twig-nesting ant colony founding and ant community assembly in a coff ee agroecosystem. I added artifi cial nests to coff ee plants in areas with and without A. instabilis four times over a year, and then examined the occupation rate and identity of species colonizing nests. I also examined vegetation characteristics of sites where nests were added. Th e presence of A. instabilis on coff ee plants drastically lowered colonization rates, but nest occupation increased with tree density, and with decreasing proportion of Inga spp. trees in the canopy. Th e presence of A. instabilis limited the number of nests occupied by six of the ten most common species; most rare species, however, were not aff ected by A. instabilis presence. Richness of colonizing ants in areas with A. instabilis was lower, but these eff ects did not signifi cantly aff ect richness across broader scales. Despite large eff ects on individual species, species composition did not diff er greatly in areas with and without A. instabilis , but some vegetation characteristics (basal area and tree richness) were predictive of ant composition. Th ese results suggest that A. instabilis strongly aff ects founding events especially for common twig-nesting species and that both vegetation and infl uences from this dominant species aff ect community assembly of twig-nesting ants at the local scale.