Behavioral Interactions in Two Ant Species in The Southeast United States and Evidence for a Native Supercolony

Ants vary extensively in their colony structure, ranging from occupying single nests to tremendous supercolonies that occupy territories spanning large areas. Fewer than 1% of ants are known to produce supercolonies, yet they are disproportionately overrepresented in highly invasive ants. A broader understanding of supercolonial ants in their native range, therefore, may provide key insights into the factors that allow some ants to become invasive. Here, we show the results of behavioral assays of two native species of ants, Dorymyrmex bureni and D. smithi (Hymenoptera: Formicidae: Dolichoderinae) across geographically separated sites in southeastern Georgia, USA. We show that D. smithi has extremely low incidence of aggression in ants from sites up to 35 km apart, indicating that this may be a supercolonial species. In contrast, we show that D. bureni exhibits high levels of aggression between nest sites. Dorymyrmex smithi is also a temporary social parasite of D. bureni and these two species form mixed nests with no apparent interspecific aggression between workers, but we show that both species interact aggressively in assays within and between sites when the workers are derived from pure species nests. These findings represent an important addition to our knowledge of supercolonial species, and they also lay the groundwork for further studies of the parasitic relationship between these species.