Figure 1

Phylogenetic tree shows the independent origin of jawed fish taar and jawless fish tarl genes. (A) A phylogenetic tree of taar and taar-like (tarl) genes was constructed using MAFFT for alignment and maximum likelihood algoritm PhyML-aLRT. For details see Methods. Clades are collapsed as indicated. A magenta/green bicolour circle denotes the ancestral node of taar-like genes (magenta, lamprey; green, cartilaginous and bony fish); a red/blue bicolour circle denotes the ancestral node of class II taar genes (red, taar13 clade; blue, taar12 clade). Representatives of all major aminergic receptor clades were used as out-group (SI Table 1), only serotonergic receptor 4, the closest relative, is shown. Numbers indicate % branch support. Scale bar, number of amino acid substitutions per site. (B) A chordate species tree with predicted gene birth events for tarl and taar clades. Presence of htr4 is denoted by filled black circles, its birth is outside the chordate clade.