Habitat structure and social behavior - the development of social phenotypes in the desert locust

Habitat structure has fundamental implications for behavior, foraging dynamics, and the social organization of animals. Locusts, which exhibit both a sedentary solitarious morph and a gregarious swarm-forming one, provide a powerful model to investigate how environmental factors shape social phenotypes. We conducted long-term continuous monitoring of locusts raised in semi-natural arenas with either clumped or distributed resources. Our findings reveal that clumped overnight roosting led to an increased propensity for coordinated marching the following day, a key precursor of swarm formation. These patterns became clearer during larval development, driving divergence in social affinity and group dynamics between habitat groups. At the molecular level, transcriptomic analysis identified a narrow set of differentially expressed genes, with enrichment in neuromodulatory and metabolic pathways, including candidates linked to monoaminergic signaling and juvenile hormone biology, such as a takeout-like JH-binding gene. These results demonstrate that spatial resource configuration is sufficient for lasting differences in individual and group dynamics and offer insight into the molecular processes mediating spontaneous, habitat-driven, phenotypic changes in a devastating plague insect.