Abstracts (first author)
King Midas meets Mendel: unraveling the genetic basis of an evolutionarily relevant color polymorphism
Color polymorphisms are tractable traits that are directly related to various crucial evolutionary processes including adaptation and speciation. The genetic basis of coloration has been the focus for genetic and evolutionary research for over a century. Despite this interest, few studies have successfully unraveled the genetic basis of color polymorphisms in natural populations; and the processes governing the origin, spread and maintenance of polychromatism are still poorly understood. The Midas cichlids of the crater lakes in Nicaragua are an excellent system to investigate the maintenance of a conspicuous color polymorphism and its role in speciation-with-gene flow. Midas cichlids are characterized by a conspicuous polychromatism: most individuals are grayish with dark bars, while some exhibit a gold coloration. The color morphs mate assortatively and have been suggested to be undergoing divergence in sympatry. Here, we explore the genetics of this trait using a combination of genetic mapping and next-generation sequencing technologies. The results show that a simple mendelian genetic architecture can underlie sympatric divergence, and might even constitute evidence for one-gene models of speciation. We further show that the onset of the phenotype is variable and dosage dependent (i.e homozygotes have earlier onset). This observation is of interest to understanding the fitness landscapes under predation pressure in the wild. The genomic region that harbors the gold locus is genomically unstable and characterized by the presence of tandem duplications and innumerous indels. The genes in the region are related to immune function, coloration and social affiliation. Patterns of association found in population-based fine-mapping using SNP genotyping and targeted-enrichment NGS are complex and compatible with multiple origins. These results indicate a role of mutation rate, hitch-hiking and pleiotropy in the maintenance of this conspicuous color polymorphism.