Abstract
Nestmate recognition, i.e., the ability to discriminate nestmates from foreign individuals, is a crucial feature of insect societies, and it has been traditionally considered to be predominantly based on chemical cues. Recent empirical evidence, however, suggests a relevant plasticity in the use of different communication channels according to cue availability and reliability in different contexts. In particular, visual cues have been shown to influence various types of social recognition in several social insects, but their role in nestmate recognition is still under-investigated. We tested the hypothesis of plasticity in the use of visual and chemical recognition cues in the primitively eusocial wasp Polistes dominula, in which the availability and reliability of recognition cues vary across the colony cycle. Indeed, before the emergence of workers, P. dominula colonies are rather small (one to few individuals), and the variability in the facial pattern might allow resident wasps to use visual cues for nestmate recognition. After workers' emergence, the increase in the number of colony members reduces the reliability of visual cues, thus leaving chemical cues as the most reliable nestmate recognition cues. We thus predict a differential use of chemical and visual cues along colony life. We experimentally separated visual and chemical cues of nestmates and non-nestmates and presented them alone or in combination (with coherent or mismatched cues) to resident wasps to test which communication channel was used in the two stages and, in case, how visual and chemical cues interacted. Our results show, for the first time in a social insect, the differential use of visual and chemical cues for nestmate recognition in two different phases of colony, which supports the hypothesis of a plastic, reliability-based use of recognition cues in this species according to the different colonial contexts.
Highlights
Social organization relies upon social recognition, which is the ability of individuals to distinguish among the individuals they encounter and to bias their behavior i.e., responding with an adaptive behavior toward the appropriate individual (Ward and Webster, 2016)
Our results show, for the first time in a social insect, a differential use of chemical and visual cues across the colony cycle, and provide the first experimental proof that, in this species, visual cues, in addition to chemical cues, are used to recognize nestmates from non-nestmates
Our results show that the relative importance of NMR cues of the two sensory modalities, visual and chemical, changes according to colony phase in P. dominula wasps
Summary
Social organization relies upon social recognition, which is the ability of individuals to distinguish among the individuals they encounter and to bias their behavior i.e., responding with an adaptive behavior toward the appropriate individual (Ward and Webster, 2016). Social recognition plays a crucial role in regulation of social interactions within animal groups, by shaping parent–offspring interactions, competitive aggression, mate choice, and cooperative behaviors (Waldman, 1988; Gherardi et al, 2012; Aquiloni and Tricarico, 2015). Eusocial insects, such as ants, wasps, termites, and bees, live in complex societies that represent pinnacles of social evolution and whose organization relies on sophisticated forms of social recognition, such as the ability to recognize caste, dominance and fertility status, gender, and nestmates from non-nestmates (Wilson, 1971; van Zweden and d’Ettorre, 2010; Cervo et al, 2015). NMR evolved to allow colony members to recognize and accept each other while strongly repelling potentially dangerous intruders, allowing the protection of the colony and directing altruistic acts toward related recipients (Hamilton, 1987)
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