Nutrient variation shapes survival without altering activity or social interaction networks in a sawfly.

Nutrient availability can shape key life-history traits including behavior. However, many studies of nutrient-dependent behavior have focused on individual activity, whereas the effects of specific nutrients on social interactions and the resulting networks remain poorly understood, especially in insects that are neither eusocial nor solitary. As major nutritional components, amino acids and carbohydrates can influence individual condition, such that variation in the nutrient availability may alter individual activity, social interactions, and ultimately lifespan. We examined how variation in either amino acids or carbohydrates influenced activity and its short-term repeatability, social interaction networks (based on mating and agonistic interactions), and lifespan in adults of the turnip sawfly, Athalia rosae, which naturally encounter heterogeneity in these nutrients across the nectar of their host plants. We provided adults with different diets spanning ecologically realistic concentrations of either amino acids or carbohydrates, and recorded adult activity over 2 d along with social interactions in mixed-sex groups. We found that neither activity nor its short-term repeatability, ie the consistency of activity across the assay days, differed across individuals from different dietary treatments. Social interactions and the resulting networks also did not differ significantly among individuals from different diets, but high-carbohydrate diets extended lifespan, whereas amino acid variation had no detectable effect on survival. These findings suggest that short-term differences in nutrient availability can influence lifespan but not individual activity or social interactions.