Plant metabolites modulate animal social networks and lifespan

Abstract

Social interactions are prevalent in animals, with some individuals participating in more interactions than others. However, the mechanisms underlying this heterogeneity in social interaction frequency and its potential fitness consequences remain poorly characterized. Here, we examine the effects of non-nutritive plant metabolites (‘clerodanoids’) on social networks and lifespan in the turnip sawfly. The adult sawflies facultatively acquire clerodanoids from non-host plant species. We found high variation in clerodanoid amounts in both wild-caught and lab-reared individuals. Furthermore, sawflies could acquire clerodanoids by nibbling on conspecifics that had prior access to these metabolites, with asymmetric clerodanoid access leading to increased agonistic interactions. Network analysis revealed more social interactions in sawfly groups where some or all individuals had prior access to clerodanoids, while groups with no prior access had fewer interactions. The number of social interactions depended on the clerodanoid status of the focal individual and also of other conspecifics. Finally, we observed a shorter lifespan in adults with prior clerodanoid access when paired with individuals without prior access, suggesting that social interactions to obtain clerodanoids have fitness costs. Our findings demonstrate that individual variation in non-nutritional sequestered plant metabolites can skew social interactions, with potential fitness implications that impact individual social niches.