The Persistence of Polymorphisms across Species Radiations

Studies on polymorphisms have been foundational to our understanding of evolu-tion. The presence of different phenotypic morphs is sometimes considered a pre-cursor to speciation in which morphs evolve into different species. While speciation should initially reduce genetic variation in daughter versus parental species, a com-mon pattern is the recurrence of the same phenotypic polymorphism in many spe-cies of a clade. Despite the ubiquity of these persistent polymorphisms, there is little discussion of their evolutionary origins. How does the genetic variation underpin-ning such polymorphisms cross speciation boundaries? What selection pressures maintain the morphs in multiple daughter species? Using diverse case studies, we highlight the characteristics of polymorphisms and selection regimes influenc-ing the likelihood of polymorphism retention across species radiations.