Behavioral interactions in two ant species in the Southeast United States and evidence for a native supercolony

Ants vary extensively in their nesting strategy, ranging from colonies occupying a single nest to colonies spread across thousands of nests. Two ant species that are native to the southeastern coastal plain of the United States, Dorymyrmex bureni and Dorymyrmex smithi (Hymenoptera: Formicidae: Dolichoderinae) have been reported to span this range of colony structures. Dorymyrmex bureni colonies occupy a single nest, while D. smithi colonies occupy many nests, ranging from hundreds to thousands. These species also exhibit a parasitic relationship with one another; D. smithi is a temporary social parasite of D. bureni and these species form mixed nests without apparent interspecific aggression. Here we provide a preliminary investigation of these two species by assessing behavioral interactions between individual nests collected from three sites that are between 3 km and 35 km apart. We test all pairwise interactions of these nests including within and between nests for each species, as well as between the two species. We show that D. smithi workers from different nests have extremely low incidence of aggression regardless of distance, potentially indicating that this species may be supercolonial. In contrast, we show that D. bureni exhibits high levels of aggression between all nests. We also show that both species interact aggressively with one another, both within and between sites, when they are not in mixed parasitized nests. These findings represent an important addition to our knowledge of ant colony structure, and they lay the groundwork for further studies of the parasitic relationship between these species.