The little fire ant: Using behavioral experimentation to understand invasive ant social structure

Wasmannia auropunctata is a small, yellow, and globally invasive ant species native to Central and South America. In non-native regions it is an established agricultural pest in addition to being ecologically destructive to local flora and fauna. It has been established in Florida for nearly 100 years. One trait thought to confer success in invasive ants is unicoloniality, which is characterized by a lack of aggression among workers and queens from different colonies. This results in colonies becoming effectively borderless, as such the lack of intraspecific aggression leads to the growth of a single, massive colony across large geographic areas. These ants are known to be unicolonial in some parts of their range, but no studies to date have assessed unicoloniality in Floridian populations. To determine whether W. auropunctata populations across Florida were members of a unicolonial lineage, pair-wise integration trials using 27 colonies from 6 sites in 3 Florida counties were carried out. Approximately 20 workers from different colonies were placed together in an arena; after 24 hours they were evaluated to determine whether colony integration occurred. From 42 trials, 17 (40%) resulted in full integration and 25 (60%) did not. Colonies collected within 9 km of each other integrated, and ants from colonies beyond that distance did not integrate. These results suggest that unicoloniality in W. auropunctata is likely spatial-scale dependent. Future studies should attempt to use colonies from more counties and incorporate genetic data to determine relatedness among these ants.