Divide and conquer: Multicolonial structure, nestmate recognition, and antagonistic behaviors in dense populations of the invasive ant Brachymyrmex patagonicus. Issue 9 (18th March 2021)

• Record Type: Journal Article
• Authors: Eyer, Pierre‐André; Shults, Phillip T.; Chura, Madeleine R.; Moran, Megan N.; Thompson, Morgan N.; Helms, Anjel M.; Saran, Raj K.; Vargo, Edward L.
• Is Part Of: Ecology and evolution. Volume 11:Issue 9(2021)
• Page Start: 4874
• Page End: 4886
• Publication Date: 2021-03-18
• Subjects: Ants -- Colony breeding system -- Invasive species -- Monogyne -- Cuticular hydrocarbons -- Aggression; Ecology -- Periodicals; Evolution -- Periodicals; 577.05
• DOI: 10.1002/ece3.7396
• Languages: English
• ISSNs: 2045-7758

Abstract

Abstract: The ecological success of ants has made them abundant in most environments, yet inter‐ and intraspecific competition usually limit nest density for a given population. Most invasive ant populations circumvent this limitation through a supercolonial structure, eliminating intraspecific competition through a loss of nestmate recognition and lack of aggression toward non‐nestmates. Native to South America, Brachymyrmex patagonicus has recently invaded many locations worldwide, with invasive populations described as extremely large and dense. Yet, in contrast with most invasive ants, this species exhibits a multicolonial structure, whereby each colony occupies a single nest. Here, we investigated the interplay between genetic diversity, chemical recognition, and aggressive behaviors in an invasive population of B. patagonicus . We found that, in its invasive range, this species reaches a high nest density with individual colonies located every 2.5 m and that colony boundaries are maintained through aggression toward non‐nestmates. This recognition and antagonism toward non‐nestmates is mediated by chemical differentiation between colonies, as different colonies exhibit distinct chemical profiles. We highlighted that the level of aggression between colonies is correlated with their degree of genetic difference, but not their overall chemical differentiation. This may suggest that only a few chemical compounds influence nestmate recognition in this species or that weak chemical differences are sufficient to elicit aggression. Overall, this study demonstrates that invasive ant populations can reach high densities despite a multicolonial structure with strong aggression between colonies, raising questions about the factors underlying their ecological success and mitigating negative consequences of competitive interactions. Abstract : Invasive ants usually form large supercolonies, in which aggression between non‐nestmates is therefore absent due to a loss of a functional chemical recognition system. Here, we investigated the interplay between genetic diversity, chemical recognition, and aggressive behaviors in an invasive population of Brachymyrmex patagonicus, an invasive ant species that surprisingly does not form supercolony. We found a high nest density despite the maintenance of colony boundaries through aggression toward non‐nestmates. This recognition and antagonism toward non‐nestmates are mediated the upkeep of chemical differentiation between colonies, with the level of aggression between colonies is correlated with their degree of genetic difference.