Nine-spined stickleback (Pungitius pungitius): an emerging model for evolutionary biology research.

The nine-spined stickleback (Pungitius pungitius) is emerging as a model for evolutionary biology, genetic, and behavioral research in the wake of its better-known relative, the three-spined stickleback (Gasterosteus aculeatus). This interest has been fed by its fascinating biological features, such as the repeated evolution of similar phenotypes in isolated pond populations. A large body of recent research has uncovered the finding that pond nine-spined sticklebacks have evolved numerous morphological, life history, neuroanatomical, and behavioral adaptations-possibly in response to reduced threat of fish predation-which differentiate them from their marine conspecifics. These features, together with insights from recent population genetic studies, suggest that this species provides an interesting model for studies aiming to understand-and differentiate between-genetic convergence and parallelism as underlying mechanism(s) of evolution of similar phenotypes in multiple independent sites. This review provides a synopsis of and reflections on the insights borne out of recent studies of nine-spined sticklebacks-the little sister of ecology's "new supermodel."