Agouti-related peptide 2 facilitates convergent evolution of stripe patterns across cichlid fish radiations.

Abstract

The color patterns of African cichlid fishes provide notable examples of phenotypic convergence. Across the more than 1200 East African rift lake species, melanic horizontal stripes have evolved numerous times. We discovered that regulatory changes of the gene <i>agouti-related peptide 2</i> (<i>agrp2</i>) act as molecular switches controlling this evolutionarily labile phenotype. Reduced <i>agrp2</i> expression is convergently associated with the presence of stripe patterns across species flocks. However, cis-regulatory mutations are not predictive of stripes across radiations, suggesting independent regulatory mechanisms. Genetic mapping confirms the link between the <i>agrp2</i> locus and stripe patterns. The crucial role of <i>agrp2</i> is further supported by a CRISPR-Cas9 knockout that reconstitutes stripes in a nonstriped cichlid. Thus, we unveil how a single gene affects the convergent evolution of a complex color pattern.