Submissive behaviour and habituation facilitate entry into habitat occupied by an invasive ant

An essential challenge in invasion ecology is discerning the role that behavioural adaptations play in competition among species. When evaluating the impacts of invasive species, the mechanisms underlying coexistence among organisms and the displacement of organisms within a community mosaic are often ignored, yet these interactions are necessary for fully understanding these impacts. Here, we examine behavioural mechanisms underlying the coexistence and subsequent displacement of an established global invader, the Argentine ant, Linepithema humile Mayr, by the newly invasive Asian needle ant, Pachycondyla chinensis Emery. In individual and group assays, we show that the numerically and behaviourally dominant Argentine ant is less aggressive towards P. chinensis workers from adjacent versus distant nests. Moreover, we show that P. chinensis displays submissive behaviour through recurrent contact with L. humile, which may contribute to the reported displacement of L. humile in the field. Understanding the factors that drive the coexistence of these two ants may help explain how small populations of a behaviourally submissive exotic species become established.