Time-scale evolutionary analyses were performed using the Bayesian Markov Chain Monte Carlo method (MCMC) with the BEAST package v1.8.3 (Drummond and Rambaut, 2007) and Tracer4 as a demographic model. Substitution models were calculated with Kakusan4 (Tanabe, 2011). The substitution model for the VP1 or the RdRp gene was the GTR-Γ or GTR-Γ invariant model, respectively. Based on Akaike's Information Criterion for MCMC values, we used the random local clock as a clock model, and used the logistic growth model (VP1 gene) or the constant size model (RdRp gene) as a tree model. Convergence was evaluated with an effective sample size (acceptable more than 200). The MCMC chain length was 3 × 108 steps with sampling every 1,000 steps for the MCMC tree of the VP1 gene. To exactly estimate the evolutionary rates and topologies of the MCMC tree of the RdRp gene, we bound two independent data of the MCMC chains5. The MCMC chain length was 2 × 108 steps and 4 × 108 with sampling every 5,000 steps for the MCMC tree of the RdRp gene. Statistical analyses were performed with the Welch's t-test in Excel 2013.