Phylogenetic analyses suggest independent origins for trichromatic color vision in apes and Old World monkeys

In catarrhine primates, trichromatic color vision is associated with the presence of three opsin genes that absorb light at three different wavelengths. The OPN1LW and OPN1MW genes are found on the X chromosome. Their proximity and similarity suggest that they originated from a duplication event in the catarrhine ancestor. In this study we use the primate genomes available in public databases to study the duplicative history of the OPN1LW and OPN1MW genes and characterize their spectral sensitivity. Our results reveal a phylogenetic tree that shows a clade containing all X-linked opsin paralogs found in Old World monkeys to be related to a clade containing all X-linked opsin paralogs identified in apes, suggesting that routine trichromacy originated independently in apes and Old World monkeys. Also, we found spectral variability in the X-linked opsin gene of primates. Our study presents a new perspective for the origin of trichromatic color vision in apes and Old World monkeys, not reported so far.