Figure 2

Vertebrate olfactory receptor gene phylogeny. a) Phylogenetic tree of all intact olfactory receptor genes identified from zebrafish (102 genes), pufferfish (44 genes), X. tropicalis (410 genes), chicken (82 genes) and human (388 genes). Branches are color-coded by species (see key). The nine major clades are labeled (α, β,γ, δ, ε, ζ, η, θ, κ); human fish-like Class I genes are within the α clade and human Class II genes are within the γ clade. Vertebrate Class II repertoire expansions include both old (e.g., human) and recent (e.g., frog and chicken; clades indicated by a-c) gene duplications. Bootstrap values are indicated at branch nodes. Figure from [15]. b) Schematic tree illustrating coalescence of human OR families (color coded branches) to the period of evolution when humans and amphibia diverged, ~370 MYA. Percent divergence is translated to divergence time by applying molecular clock estimates. Taxonomy: Pisc = fish; Amphibia = frogs, salamander; Aves = chicken; Proto = platypus; Meta = koala; Sci = marmot, mouse, rat; Fer: pig, dolphin, dog; Strep = lemurs, squirrel monkeys, Plat = marmoset; Cer = baboon, macaques; Hom = chimpanzee, gorilla. Figure reprinted from [19], Copyright (2001), with permission from CSH Press.