Colony recognition and aggression in invasive Argentine ants of Georgia

REU Fellow: Paige Caine, Bucknell University

Mentor: Dr. Joshua Gibson

An invasive species with introduced ranges worldwide, Argentine ants outcompete local ant species, instigating potentially drastic changes in their introduced ecosystems and threatening the Georgia intercoastal plains. One factor enabling their success is the formation of “super-colonies” in introduced ranges, including a global supercolony with members across California, Japan and Europe. Though in their native range each colony aggressively defends one small territory from other colonies, this aggression occurs less in introduced ranges. Because Argentine ants recognize colony-mates by smelling hydrocarbons embedded in each ant’s cuticle, and we believe hydrocarbon differences are genetically based, one hypothesis for why Argentines form supercolonies invasively and not natively is that a genetic bottleneck occurred during introduction to new ranges, causing a subsequent loss in cuticular hydrocarbon diversity in introduced populations. This would limit each colonies’ ability to distinguish outsiders, and may be responsible for supercolony formation. To test this, we collected Argentine ants from 6 nest-sites across Georgia, extracted DNA from members of each nest-site, and amplified 8 microsatellites in order to understand our populations’ genetic history. We also ran behavioral assays, pairing ants randomly and observing interactions for three minutes. By combining the behavioral and genetic data, we hope to understand how genetic diversity affects aggression.