The genetics, evolution, and maintenance of a biological rock-paper-scissors game.

Side-blotched lizards (Uta stansburiana) play a biological rock-paper-scissors game in which three differently colored male morphs utilize alternative mating strategies. We identified the genetic basis of this polymorphism, which was previously posited to arise from three alleles at one locus. Orange usurper and blue mate-guarder morphs are associated with two divergent haplotypes in the regulatory region of the sepiapterin reductase gene, but yellow sneaker morphs appear to arise through phenotypic plasticity from the same genetic background as blue morphs. Our simulations show that rock-paper-scissors dynamics can better maintain a polymorphism with a genetic system of two alleles plus plasticity than with a three-allele system. This form of balancing selection that combines genetic determination with phenotypic plasticity expands the possibilities for how stable polymorphisms arise in nature. Editor's summary: Many animal species exhibit different physical characteristics between individuals, especially when it comes to males. Lizards are particularly interesting examples, because many species have multiple versions of males. Studying these species can inform understanding of how such polymorphism evolves and operates. Uller et al. found that a recently emerged white throated morph of European wall lizards was highly preferred over an earlier three-color system, which has led to disruption of a million-year balance across the morphs (see the Perspective by Gopalan and Castoe). In related work on side-blotched lizards in the United States, Corl et al. found that a well-known morphological triad of males was generated by a two-allele system, with phenotypic plasticity at one of the alleles and a rock-paper-scissors dynamic. —Sacha Vignieri [ABSTRACT FROM AUTHOR]