Global Organization and Proposed Megataxonomy of the Virus World

Interesting paper on a sort of bird’s eye view of virus evolution across the history of life, and an attempt to come up with a system of viral taxonomy encompassing all viruses.

The Ultimate Network Architecture of the Virus World
The final question that we must address here is whether evolutionary connections across the entire virus world exist that would make the megataxon “Viruses” a legitimate concept. As discussed above, some major groups of viruses, for example, the two realms of dsDNA viruses, do not share an ancestry. Yet the matter is not unambiguous. Indeed, three simple protein domains that are present in multiple (super-)VHGs, namely, (i) the RNA recognition motif (RRM) that forms the cores of all virus polymerases; (ii) the jelly roll, the core domain of SJR- and DJR-MCPs; and (iii) S3H, the replicative helicase of diverse viruses, link the majority of the viruses in all BCs and in three of the four proposed realms (Fig. 12) (80). Thus, underneath the vastly different evolutionary histories and the polyphyly of viruses, fundamental structural and evolutionary unity likely harkens back to the primordial pool of genetic elements. In particular, primordial RNA replicons, including reverse-transcribing replicons akin to extant group II introns, were the likely ancestors of the realm Riboviria (80).

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Edited link, should be free access to full article now.

Edit2: It seems the publisher has taken the article off free access now.

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I’m not sure about this thesis. Aren’t some viruses of independent origins, from non viral starting points with a common origin?

I suppose they call it “polyphyletic”, but how does that produce a mega taxonomy?

Yes, they say as much.

Taxonomy essentially just refers to classification. So a classification of viruses, even if different viruses arose independently, would still amount to a “taxonomy” of viruses.

As they explain in the part I quoted above, they think the category “Viruses” is a legitimate concept because, as even though all viruses don’t share common ancestry and some clades appear to have originated independently from cellular life at different times, they still have a handfold of shared protein domains that define and link them together.

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