Data from the paper: 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. This polymorphsim was previously posited to arise from three alleles at one locus. We identified the genetic basis of this polymorphism, using genome-wide association studies. Orange usurper and blue mate-guarder morphs were associated with two divergent haplotypes in the regulatory region of the sepiapterin reductase gene, but yellow sneaker morphs appear to arise via phenotypic plasticity from the same genetic background as blue-morphs. We aligned genome assemblies for an orange and blue-morph to determine that the associated genetic region was not in a chromosomal inversion. We studied the genetic diversity of the morph-associated region and found that it had elevated nucleotide diversity, consistent with balancing selection. We used RNA-seq data to show that there were difference in gene expression among the morphs. We tested the predictions of the two and three-allele models against data from field surveys of the polymorphism and found that the two-allele model provided a better fit to the field data.

We updated the models of the maintenance of the polymorphism to fit our new genetic understanding of the system. We found that a variety of different models maintained the polymorphism, some of which gave rise to frequency-cycles. We also conducted a game theoretical analysis of the conditions that lead to a stable polymorphism. In addition, we added genetic drift to our population genetic models to study how well they are able to maintain the polymorphism. Our simulations showed 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.