(ω) ratios of genes in the CPXV genome . The ratio for the gene is the average ω of all codons in the gene. Black: Genes with sites under diversifying selection (Genes for which the alternative model, allowing positively sites with ω>1, fits the data better than the null model (p < 0.05)). White: Genes without sites under diversifying selection. A) Ratios determined using model M2a, with statistical significance determined by comparison with M1a. B) Ratios determined using model M8, with statistical significance determined by comparison with M7.