Figure 2

Evolutionary changes in the number of T2R genes in mammals. The phylogenetic tree and the divergence times were obtained from Murphy et al. [28] and Glazko et al. [29]. The numbers to the right of each black dot indicate the numbers of genes in the common ancestral species. The numbers below or above each branch indicate the numbers of gene gains and losses, respectively. The red arrows represent gene expansions and the green arrows represent gene contractions.