Dominance of a highly invasive ant is limited to the nesting territory of its supercolony

Abstract

Ant invasions represent a serious threat to biodiversity, agriculture and public health. Highly invasive ant species exhibit a very high abundance within its introduced range and cause severe impacts on native ant communities. This scenario tends to be different within the native range, where competitor ants may limit its access to food sources, thus its abundance. Here, we evaluated the competitive ability of a typical clonal and supercolonial native population of Wasmannia auropunctata (Roger) (Hymenoptera: Formicidae) in Argentina. We used a combination of pitfall traps and food baits to study the ant interactions within an assemblage where W. auropunctata coexists with another great invader, Solenopsis invicta (Buren) (Hymenoptera: Formicidae). The studied assemblage presented 56 ant species/morphospecies. Although W. auropunctata was the most abundant numerically, its ability to discover baits was intermediate, and its ability to recruit workers massively and monopolise baits was low. Wasmannia auropunctata was not successful defending baits nor attempting to usurp baits dominated by other species. Moreover, it lost all contests against S. invicta, one of the most ecologically dominant species in this assemblage. Wasmannia auropunctata dominated food sources only when they were located within the nesting territory of its supercolony. Within the native range, clonality and supercoloniality may favour the local numerical abundance of a highly invasive ant but may not be enough to achieve ecological dominance. This study sheds light on the important role of biotic interactions as a key factor that may limit the dispersal of invasive species.