Gene expression analysis of 6 DGRP lines based on clustering behavior and housing

Emerging evidence indicates that Drosophila establishes social networks in groups, yet how flies shape social distancing remains poorly understood. Here we demonstrate a negative correlation between social-network behavior (SNB) and aggression. We developed a systemic SNB analysis that quantifies individual social distances and group behaviors over time. Quantitative assessment of SNB in 176 inbred lines from the Drosophila Genetics Reference Panel revealed a tight association of low SNB with hyperactivity and highly aggressive behavior. Social isolation during development was sufficient to suppress high SNB, whereas it rescued low SNB lines with relevant changes in aggression behaviors. The early-life experience-dependent plasticity of SNB required the neuropeptide Drosulfakinin (Dsk) important for aggressive behaviors since Dsk mutants displayed constitutively high SNB regardless of social isolation. Given the conserved role of a Dsk homolog, cholecystokinin, in mammalian social behaviors, we propose that animals have evolved a dedicated neural mechanism for adaptively balancing SNB and aggression, thereby manipulating group properties for physiology and fitness.