Evolutionary comparison of homologous gene clusters containing gamma-OR genes in a subset of FAN species (one per taxonomic order), showing the highest number and proportion of this receptor subtype in the bichirs. Analysed teleost species present reduced or absent gamma-OR repertoires, restricted to a unique gene cluster. Left, pairwise sequence identity (PSI) at the protein level between receptors from the largest gene OR cluster in the ropefish (E. calabaricus). Regions containing gamma-OR genes are marked. Middle, boxes represent the relative size of gene clusters homologous to those containing gamma-ORs in the bichirs. The proportion of gamma-ORs (hatched) is also at scale. The third round of whole genome duplication (3R-WGD) at the base of the teleost clade and a genomic rearrangement (gr.) in clupeocephalans are indicated. The proportion of gamma-OR in pie charts is calculated over the complete OR repertoire in each species. Dominant gamma-OR proportion in an amphibian outgroup is also shown (Xenopus tropicalis). E. calabaricus and Xenopus silhouettes were downloaded from http://phylopic.org/ .
