Fig. 4

A timetree inferred using the reltime method and the general time reversible model of fish T1R2 genes. The timetree was computed using 4 calibration constraints. The estimated log likelihood value is − 21,587.6247. A discrete Gamma distribution was used to model evolutionary rate differences among sites (5 categories (+G, parameter = 1.6461)). The rate variation model allowed for some sites to be evolutionarily invariable ([+I], 9.5713% sites). The analysis involved 30 nucleotide sequences. All positions containing gaps and missing data were eliminated. There were a total of 1353 positions in the final dataset. Evolutionary analysis was conducted in MEGA7. The T1R2s nucleotide sequences of fishes used are given in the electronic Additional file 4: Table S3