Seasonal nestmate recognition in the polydomous ant Plagiolepis pygmaea

Nestmate recognition cues can derive from genetic and/or environmental factors and can be contextdependent rather than fixed over time. We examined the influence of genetic relatedness and environment on nestmate recognition and its seasonal variations in a natural population of the polydomous (multiple-nests per colony) ant Plagiolepis pygmaea in southern France. Recognition between colonies was measured by testing aggression levels during encounters between five workers of colony A and one of colony B and vice versa. The combination of genetic data, spatial data and aggressive behaviour data shows that nestmate recognition cues have principally a genetic component. Whereas workers from different nests of the same colony are never aggressive to each other, they are always hostile to alien conspecifics regardless of the spatial or genetic distance between the colonies. Our results also reveal significant seasonal variations in the levels of aggression among workers of different colonies, probably according to the biological cycles of the species. Surprisingly, despite the mode of colony reproduction being budding in P. pygmaea, the population of Tarabel is not genetically structured.