Nonparametric tests of association between dN and Dr/Dc, calculated under four classification schemes: charge, polarity, the scheme of Miyata et al. [56] (MY), and the scheme of Hanada et al. [57] (HAN).

Spearman's rho (rs) was used to quantify the strength and significance of the association. Boldface values indicate the classification scheme showing the strongest positive association with dN for a given genome pair. Within each pairwise comparison, proteins were filtered to remove those with zero radical and/or zero conservative amino acid changes under any of the four classification schemes for that particular pairwise comparison.