Bacterial biofilms dominate microbial life; however, their evolutionary genetics remain incompletely understood. Extensive replication of biofilm selection experiments by secondary school students can provide valuable insights into mechanisms of adaptation. Notably, mutations in a conserved phosphodiesterase, PFLU0185/bmo, dominate evolved populations without changing colony morphology. Phenotypic assays reveal that bmo plays a generalist role and competes with its ancestor and other diverse, less frequent biofilm-specialist mutants, resulting in populations that have differentiated to fill multiple niches within the biofilm life cycle. This work also demonstrates the power of distributed research networks for addressing complex biological questions while promoting scientific literacy to the public.