Community organization in a recently assembled fauna: the case of Polynesian ants.

The ant species inhabiting three remote Polynesian islands were censused by hand collecting techniques. Three commonly occurring species, which exhibited complementary distribution patterns, were numerically and behaviorally dominant to other species in the communities in which they occurred. Field observations and laboratory experiments showed that negative interspecific interactions were important in maintaining the exclusive territories of the dominant species. Habitat also played a role in determining the distribution of dominant species. Pairwise tests of association among all species revealed dominant species were commonly positively associated with their own non-overlapping group of subordinate species, forming a large-scale mosaic distribution pattern of dominant and subordinate species. Baiting experiments, conducted with and without the dominant species removed, demonstrated that the presence of the dominant species decreased: (1) the proportion of baits occupied by other species, and (2) overall ant species diversity, at rich food resources. In ant communities where one of the three recognized dominant species was present, the outcome of negative interspecific interactions among species was more predictable than in communities without a recognized dominant. The same patterns were evident regardless of which of the three dominant species was present in the community. These patterns of community organization observed in this relatively newly assembled fauna are very similar to those reported from studies of older ant communities in mainland areas.