UC Santa Cruz

Many factors drive the organization of communities including environmental factors, dispersal abilities, and competition. In particular, ant communities have high levels of interspecific competition and dominance that may affect community assembly processes. We used a combination of surveys and nest supplementation experiments to examine effects of a dominant groundânesting ant (Pheidole synanthropica) on (1) arboreal twigânesting, (2) groundâforaging, and (3) coffeeâforaging ant communities in coffee agroecosystems. We surveyed these communities in highâ and lowâdensity areas of P. synanthropica over 2 years. To test for effects on twig ant recruitment, we placed artificial nesting resources on coffee plants in areas with and without P. synanthropica. The first sampling period revealed differences in ant species composition on the ground, in coffee plants, and artificial nests between highâ and lowâdensity sites of P. synanthropica. Highâdensity sites also had significantly lower recruitment of twig ants and had speciesâspecific effects on twig ant species. Prior to the second survey period, abundance of P. synanthropica declined in the highâdensity sites, such that P. synanthropica densities no longer differed. Subsequent sampling revealed no difference in total recruitment of twig ants to artificial nests between treatments. Likewise, surveys of ground and coffee ants no longer showed significant differences in community composition. The results from the first experimental period, followed by survey results after the decline in P. synanthropica densities suggest that dominant ants can drive community assembly via both recruitment and establishment of colonies within the community.