Prey handling performance facilitates competitive dominance of an invasive over native keystone ant

Studies of species coexistence in ant communities often suggest that competitive interactions are mediated by behavioral trade-offs between resource discovery and dominance. However, these studies have always measured foraging at artificial, static baits that omit traits of living prey items and potential coevolutionary predator–prey relationships. In a series of lab experiments, we compare the ability of ants to harvest live termites (Reticulitermes virginicus) in nests varying in defensive ability. Moreover, we compare foraging performance of 2 co-occurring ant species—the North American native Aphaenogaster rudis and the invasive Pachycondyla chinensis—differing in their evolutionary experience hunting R. virginicus. Our results show how the invasive P. chinensis may displace the native keystone A. rudis by directly killing A. rudis workers and reducing termite prey available for A. rudis. Specifically, P. chinensis is more sensitive to novel termite prey than the native A. rudis and then destroys termite colonies—even if they are highly defended by soldiers or nest architecture. Our results further show how whole colony behavioral dominance by P. chinensis is mediated by behavioral interactions among individual workers. More generally, our experimental approach using live prey to study interspecific competition can integrate evolutionary dynamics into studies of proximate behavioral factors governing species coexistence.