The genetic basis of a colorful signal: the polymorphic dewlap of the slender anole (Anolis apletophallus)

Organisms often use colorful morphological traits to communicate with members of their own or other species. While “colorful signaling” systems exemplify well-known examples of the evolution of phenotypic diversity, the genetic basis of most of these traits remains unknown. Male lizards of the genus Anolis possess a colorful throat fan, or ‘dewlap’, that is flashed during social displays. These displays have been extensively studied in the context of their role in the adaptive radiation of the genus. In contrast, the genetic basis of the Anolis dewlap has received relatively little attention. Here, we studied the dewlap of the slender anole (Anolis apletophallus) which exhibits a dewlap polymorphism: males have either an entirely orange dewlap (“solid” morph) or a white dewlap with a basal orange spot (“bicolor” morph). To understand the inheritance of this polymorphism, we conducted 99 crosses between individuals from populations that were fixed for one morph (single/fixed/monomorphic) or contained both morphs (mixed/polymorphic). Next, we investigated the genetic architecture of this trait using a pooled population sequencing (Pool-seq) experiment. Our findings indicate that the slender anole dewlap polymorphism is best explained as an autosomal, single-locus, Mendelian trait with the solid morph allele dominant to the bicolor morph allele. Our outlier analysis of the Pool-seq data identified a region strongly associated with this trait and within this region we identified a promising candidate locus—the transcription factor single-minded 1 (SIM1)—that may underly the dewlap polymorphism.