Fig. 4
From: Expanded olfactory system in ray-finned fishes capable of terrestrial exploration
γ-OR genes scarcity in amphibious teleosts after gene cluster loss. a Evolutionary comparison of homologous gene clusters containing γ-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 γ-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 γ-OR genes are marked. Middle, boxes represent the relative size of gene clusters homologous to those containing γ-ORs in the bichirs. The proportion of γ-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 γ-OR in pie charts is calculated over the complete OR repertoire in each species. Dominant γ-OR proportion in an amphibian outgroup is also shown (Xenopus tropicalis). E. calabaricus and Xenopus silhouettes were downloaded from http://phylopic.org/. b Boxplots showing gene numbers for each of the OLF receptor families separately. Taking into account phylogeny (PGLS), significant differences are detected between FAN species (n = 10, Additional file 2: Table S8) versus the rest (n = 192) in three out of four OLF gene families (OR, TAAR and V1R). c Diagram depicting those OLF gene families particularly expanded in different FAN lineages (according to outlier species in Additional file 1: Fig. S2a and Fig. 3e). One representative organism for each taxonomic family that includes FAN species is shown. Gray boxes mark relevant events with potential influence in the proposed evolutionary scenario. A red star is used to reference the largest OR gene cluster found in the bichirs. Tetratpoda, L. chalumnae, L. oculatus, M. cyprinoides, A. melas, S. orbicularis and B. splendens silhouettes were downloaded from http://phylopic.org/