Origins and Evolution of the Global RNA Virome

Yuri I. Wolf; Darius Kazlauskas; Jaime Iranzo; Adriana LucÍa-Sanz; Jens H. Kuhn; Mart Krupovic; Valerian V. Dolja; Eugene V. Koonin

We made an attempt to quantify the potential horizontal virus transfer (HVT) events in RNA 647 viruses that represent the 5 major branches of the RdRp tree. The leaves of the tree were labeled 648 with the known hosts, the entropy of the host ranges for each subtree was calculated, and the 649 resulting values were plotted against the distance from the root (Figure 9 ). By design, for all 650 branches, entropy (host diversity) drops from the maximum values at the root to zero at the 651 leaves. All branches show substantial host range diversity such that, for example, at half-distance 652 from root to leaves, all branches, except for Branch 1, retain at least half of the diversity (Figure 653 9). Furthermore, differences between the branches are substantial, with the highest entropy 654 observed in branches 4 (dsRNA viruses) and 5 (-RNA viruses). With all the caveats due to 655 potential errors and ambiguities in host assignment, this analysis strongly suggests that HVT 656 played an important role in the evolution of all major groups of RNA viruses. 657