Social network differences and phenotypic divergence between stickleback ecotypes.

This article investigates the role of social behavior in the divergence between two marine ecotypes of three-spined stickleback fish (Gasterosteus aculeatus), known as "whites" and "commons," using social network analysis. The study found that juvenile whites are bolder and more active than commons and that groups of whites exhibit lower clustering coefficients, indicating more cliquish social networks, compared to commons. However, no assortative shoaling preferences were detected, as individuals did not preferentially associate with their own ecotype in mixed groups, where social network structure resembled that of commons. These findings suggest that early-life differences in social network structure may contribute to population divergence and reproductive isolation, highlighting the utility of social network analysis in understanding ecological and evolutionary processes.