The variability of iridomyrmecin, the venom of the Argentine ant, in its native and invasive ranges

The Argentine ant is one of the five worst invasive ants. Recently it has been shown that one of the main compounds of its pygidial gland, iridomyrmecin, is used as a venom against competitors and enemies. Here, we explore the variability in the quantities of iridomyrmecin of individual workers, along a range of locations pertaining to both its native and invasive ranges, in order to know whether its venom could have contributed to the differential invasion success of European supercolonies. We specifically compared the amount of iridomyrmecin among supercolonies in the native range and among three invasive supercolonies: the Main supercolony (the most extended worldwide), the Corsican and the Catalonian supercolonies (both with a restricted distribution in Europe). Our main result is that the variability of the iridomyrmecin is very high. Looking at mean values, we found that the amount of iridomyrmecin of the Main supercolony was the lowest while the highest corresponded to the Corsican supercolony, with the Catalonian and the native range supercolonies having intermediate values. However, variability in the values within each supercolony was similar between supercolonies. This suggests that the success of a given invasive supercolony may not be explained by higher quantities of this defensive compound. Our results open the way for exploring the connection between defensive compounds and the invasion success of this global invader.