Individually distinctive facial patterning without a signal value: a case of ‘missing’ social knowledge in the paper wasp Polistes versicolor?

Abstract

Inter-specific variation in the occurrence of individual recognition (IR) has mostly been examined in species that differ with respect to two critical conditions necessary for such ability: presence of complex social behaviours and sender’s distinctiveness. However, variation in IR when species share such conditions is lesser known. We tested for IR in the paper wasp Polistes versicolor and compared the results with published information on IR in Polistes fuscatus. Both species have a flexible nest-founding behaviour and form dominance hierarchies. Additionally, both have individually distinctive facial patterns. P. versicolor faces are highly variable, and they do not appear to be associated with individual quality, consistent with the role as cues in IR. However, the wasps did not discriminate between nestmates with familiar and unfamiliar faces. Besides, wasps did not discriminate between familiar and unfamiliar social partners. Familiar discrimination (discrimination of individuals based on prior social interactions) is considered the first stage toward IR; therefore, P. versicolor wasps, unlike P. fuscatus, lack the ability for IR. Our results suggest that the high variation in colour pattern may not be a good proxy for the occurrence of IR in paper wasps and that neutral variation may be an underestimated factor promoting phenotypic variability. High inter-individual phenotypic variability in primitively eusocial paper wasps has sometimes been considered to be a result of selection for efficient individual identity signalling, especially because senders may benefit from being individually recognised. P. versicolor paper wasp females have highly variable inter-individual facial patterns. However, we demonstrated that they lack individual recognition. After excluding some potentially confounding hypothesis, we conclude that selection for efficient individual identity signalling is not the only factor promoting phenotypic variability in paper wasps and that at least in some species, neutral variation may play a role.