Can alternative pathways mediate the influence of queen number on nestmate discrimination in ants?

The evolution of social life is usually associated with capabilities of individuals to protect group boundaries against foreign individuals. In colonies of ants, the number of reproductive queens is known to influence the accuracy of nestmate discrimination by resident workers. However, the pathway by which this effect is mediated remains unclear. The major hypothesis has long been that workers from multiple-queen colonies commit more discrimination errors against foreigners because their colonies contain a broader diversity of genetically determined cues characterising colony membership. Until recently, this hypothesis has received little attention and poor empirical support. In a recent study, Meunier et al.1 proposed an alternative, albeit not mutually exclusive hypothesis. The presence of one or multiple queens modifies chemical signals on colony members that trigger aggressive or cooperative behaviors during foreign encounters. Here, I detail how this new hypothesis is congruent with previous results and discuss potential limits and evolutionary implications of the two suggested hypotheses.