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Genes and the environment jointly shape individual traits, but the influence of indirect genetic effects (IGEs), arising from the genetic composition of interacting conspecific individuals, is often ignored or underemphasized. Moreover, because of practical challenges in characterizing IGEs, empirical research has fallen behind theoretical advancement. The fire antSolenopsis invictaoffers a uniquely suitable study system due to its distinct colony-level phenotypic variation (monogyne and polygyne social forms) attributed to IGEs of a social-supergene variant (ballele). A minority ofb-carrying workers (Bbgenotype) can trigger colony-level conversion from monogyne (single queen per colony) to polygyne (multiple queens per colony) behavior. This study investigated the mechanisms underlying this process via 400-ant microcolonies. We first showed that assimilatedBbworkers reduce aggression by hostBBworkers towardBbqueens, thus inducing polygyny, at rates observed earlier in experiments that used full-size (>20,000 ants) colonies. We then demonstrated that social conversion is facilitated by cuticular contact between the worker types, and verified the presence of nonvolatile cuticular pheromones that are necessary but not sufficient components underpinning this process. Follow-up experiments suggested that a second, polygyne worker-produced pheromone that is only released once such workers detect aBbqueen is also necessary but again insufficient, for full expression of the conversion phenomenon. Thus, multiple pheromonal components linked to presence of thebsupergene allele in colony workers appear to be involved in shaping social environments and thereby inducing, via IGEs, the transformation from monogyne to polygyne fire ant societies. 

Reversal learning has been studied in many species, often as an indicator of their behavioral flexibility. Although this research typically focuses on individuals, groups of social animals, especially social insects, are often considered to have similar learning capabilities. Associative learning has been rarely studied in ant colonies and their behavioral flexibility is still to be assessed. In this study, ant colonies readily learned to discriminate between compound visuotactile cues and subsequently learned their reversal. Reversal performance was maintained after a 5-day retention interval, but not after a 10-day interval. Although this study does not differentiate learning processes at the individual vs. colony levels, it is the first demonstration of reversal learning conducted in ant colonies. These results show that the two-corridor maze can serve to assess colony-level learning in ants. This is a first step to investigate key mechanisms underlying collective learning and cognition in ants.