Monophyletic origin of the T2R and the V1R/ORA receptor family. The phylogenetic tree was generated using a maximum likelihood method (PhyML-aLRT) with SPR setting for tree optimization and chi square-based aLRT for branch support (given as percentage). Branches are color-coded for the respective species (Latimeria chalumnae, purple; mouse, dark green; Xenopus tropicalis, light green; lamprey, blue; 5 teleost fish species [zebrafish, stickleback, medaka, fugu, tetraodon], red). t2r of all species form a single subclade, as do all v1r genes. Grey filled circles indicate clades analysed for evidence of positive selection, see Figure 5. Gene sequences for Xenopus tropicalis and teleosts were taken from  for T2Rs and  for V1R/ORAs.