Overall evolutionary rates for P1 and VP1 regions were measured as the number of nucleotide substitution per site per year (s/s/y). Relevant parameters were summarized as the median of posterior distributions by Bayesian coalescent Markov chain Monte Carlo algorithm implement in the Bayesian Evolutionary Sampling Trees (BEAST) software package version 1.4.8 [31] . To identify the optimal substitution model we performed a maximum likelihood analysis using the Modelgenerator package [35] . The model that best fit both sequence datasets was General Time Reversible (GTR) model with a discretised γ-distribution (GTR+Γ), allowing for nucleotide rates to vary among sites within the protein coding sequence alignments. Codon partitions (1+2)+3 were applied to both alignments, keeping first and second positions (mostly to non-synonymous changes) in one partition and the third position (related to increase redundancy and prone to synonymous changes) in a separate partition [36] . Relative rate parameters were estimated in separate for each partition, in order to accommodate rate variation at the third codon position.