Revisiting rapid phenotypic evolution in sticklebacks: integrative thinking of standing genetic variation and phenotypic plasticity

Phenotypic evolution can result from new mutation, standing genetic variation, or phenotypic plasticity. Extensive reviews have focused on either comparing phenotypic evolution by new mutations vs. standing genetic variation (Barrett and Schluter, 2008) or the effect of phenotypic plasticity on generating biodiversity (Moczek, 2010; Pfennig et al., 2010; Moczek et al., 2011). This article focuses on discussing the potential integrative effect of standing genetic variation and phenotypic plasticity on rapid phenotypic evolution. I start with comparing and contrasting how standing genetic variation and plasticity promote phenotypic evolution and conclude by illustrating three examples in threespine sticklebacks—variation in number of lateral plates, the existence of pelvic girdles, and alternative foraging forms—to demonstrate that both mechanisms could be involved in the same pattern of rapid phenotypic evolution, even though in these cases only one mechanism was invoked by the authors to explain the pattern.