Recognition without aggression: divergent regulation of food sharing in Argentine ant supercolonies

The Argentine ant (Linepithema humile) is a globally invasive species with major ecological and economic impacts, often displacing native fauna and disrupting ecosystems. Its success is linked to a unicolonial structure, where vast supercolonies span thousands of kilometers and ants from different nests coexist without aggression. In Europe, for example, one supercolony stretches over 6,000 km from Italy to the Spanish Atlantic coast. Despite this apparent unity, neighboring nests show subtle genetic and chemical differences, raising the question of whether ants can recognize individuals from other nests within the same supercolony, and whether such recognition influences cooperation, particularly food sharing. We tested this in both a native population (Argentina) and an invasive one (France), combining behavioral assays of food exchange with cuticular hydrocarbon profiling. Argentine ants in both ranges discriminated between nestmates and non-nestmates within supercolonies, but the bias was expressed only during early interactions and did not escalate to aggression. Native ants showed more state-dependent and delayed transfer, whereas invasive ants engaged earlier and involved more partners, revealing distinct regulatory architectures of food sharing. Chemical analyses of cuticular hydrocarbons confirmed that different nests, even when belonging to the same supercolony, remain chemically distinct in both native and invasive ranges despite the absence of aggression. These findings suggest that unicoloniality stems from relaxed acceptance thresholds rather than a collapse of recognition. Our study has implications for invasion biology and management, since the efficiency of toxic baits depends on uniform food distribution. If recognition biases resource sharing, both colony organization and control strategies may need reconsideration.