FIG 1 .
Evolutionary dynamics of the major capsid protein of GII.2 noroviruses. (a) Maximum likelihood phylogenetic tree of VP1-encoding (nt) sequences from GII.2 strains. The numbers on the ancestral nodes of the clusters represent the node support value calculated by the approximate likelihood-ratio test using PhyML. (b) Root-to-tip divergence plot of VP1 nt sequences of GII.2 strains. The x axis indicates isolation year, and the y axis shows the root-to-tip divergence on the maximum likelihood phylogenetic tree. The black line indicates a linear regression line of the root-to-tip divergence and isolation year. A total of 151 sequences were included for both analyses. Each strain is represented by a circle and colored according to its polymerase genotype. Strains whose polymerase genotype was not available are indicated in black. The genomic region used in the analyses spanned nt 5085 to 6419 relative to Snow Mountain virus (GenBank accession number AY134748). (c) The kernel density plot indicates the posterior estimates of substitution rate (substitutions/site/year) of VP1 nt sequences. To calculate the substitution rate of the VP1 associated with different polymerases, strains were clustered using the VP1 phylogenetic tree. Thus, the P2 cluster is shaded in red, the P16 cluster in green, and the P2-P16 mix in yellow. The overall rate is indicated by black shading.