Figure 4

The evolutionary scenario of OR genes in chordates[14, 37]. Phylogenetic analyses suggested that the divergence between type 1 (circles) and type 2 (triangles) occurred before the divergence between jawless and jawed vertebrates, and the divergence among groups α - ζ (circles in different colours) predate the divergence between teleost fish and tetrapods. In terrestrial organisms, group α (red circles) and γ genes (blue circles) have largely expanded.