Figure 6. A schematic presentation of the evolution of GPCR mediated chemosensory gene families.

The eukaryotic evolutionary tree is constructed with references from the tree of life web project (http://tolweb.org/tree/phylogeny.html). Each gene family is represented with colored symbols and their presence and absence were mapped onto eukaryotic branches. A red arc represents the hypothetical origin of the gene families. The hypothetical origin of these gene families including, chordate like olfactory receptor family, vomeronasal type 1 family and taste 2 receptors were obtained from previous studies [2], [16], [18], [22], [24]. Branch lengths are not drawn to represent actual evolutionary distances.