Transitions and transversions versus divergence plots. The estimated number of transitions and transversions for each pairwise comparison was plotted against the genetic distance calculated with the TN93 model  for (1) dataset A, (2) dataset B, (3) exonic sequence, (4) intronic sequence. Transitions outnumber transversions along with the linear increase in the genetic distance. This pattern can be interpreted as indicating that substitution saturation has not been reached, so that the data can be expected to provide sufficient phylogenetic signal.
Christelová et al. BMC Evolutionary Biology 2011 11:103 doi:10.1186/1471-2148-11-103