Mismatch distribution of cluster IV strains for the concatenated sequences (sSNPs). These curves represent the frequency distribution of pairwise differences. The dashed plot correspond to the observed data; the smoth curve corresponds to the sudden expansion model and the punctuated lines represent the upper and lower bounds of the 95% confidence interval on this model. P value represents the probability that the raggedness of the simulated data set is equal to or greater than the observed data set. The major demographic extension occurred 2 mutations ago for the entire concatenated genes (70 kb). The latter translates into 0.003% sequence divergence, which suggests that the maximum population expansion occurred about 3,300 years (700 to 7,200 years) ago.