Figure 2.

Two approaches to the calculation of the evolutionary age of TBEV. (A) Assuming the hypothesis of gradual evolution (genetic distances are calculated between “clusteron-founders” and putative common ancestor). The age of a branch corresponds to the age of the ancestor. (B) Assuming the hypothesis of quantum evolution resulting in a dramatic change of genetic features and nonlinear accumulation of mutations (genetic distances are calculated within “clusteron-founders”). TBEV subtypes or lineages are likely to emerge not from the putative ancestor but rather directly from the existing viral forms.