Fisher's exact test for amino acid changes at NCGN sites and non-CpG sites.

The abbreviated species names are as indicated in Table 1 and substitution types have been described in Figure 1. The results were obtained using homologous fragments from the species pair. Amino acid changes were collected at NCGN sites and other sites. Nonsynonymous substitutions responsible for the amino acid changes at NCGN sites include TG, CA, M1 and P1 substitutions. The numbers from species X and Y for Non-CpG and NCGN were used to constitute 2×2 contingency table. *, P<0.05; **, P<0.01; ***, P<0.001.