ML estimates of the present models with the respective selective constraints for the 1-PAM amino acid substitution matrices of JTT, WAG, and LG.

aIn all models, equal codon usage () is assumed. If the value of a parameter is parenthesized, the parameter is not variable but fixed to the value specified.b for JTT, for WAG, and for LG.c #parameters with for JTT, for WAG, and for LG; see text for details.dNote that these ratios are not the ratios of the rates per site but per codon; see text for details.