Estimating evolutionary rates in giant viruses using ancient genomes

Area of Science:

• Virology
• Evolutionary Biology
• Genomics

Background:

• Pithovirus sibericum, a giant DNA virus from ancient permafrost, and Pithovirus massiliensis from France, were compared.
• Initial studies suggested a rapid evolutionary rate for Pithovirus, nearing that of some RNA viruses.

Purpose of the Study:

• To reassess the evolutionary rate of Pithovirus.
• To determine a more biologically plausible timescale for Pithovirus evolution.

Main Methods:

• Utilized the inverse correlation between genome size and evolutionary rate in DNA viruses.
• Applied time-dependent evolutionary rate models.

Main Results:

• A more plausible evolutionary rate for Pithovirus is estimated at approximately 2.23 × 10^-6 nucleotide substitutions per site per year.
• This rate is at least an order of magnitude slower than previously suggested.
• Inferred divergence times suggest Pithovirus evolved over hundreds of thousands of years.

Conclusions:

• The evolutionary rate and timescale of Pithovirus require re-evaluation.
• Future giant virus evolution rate estimates should consider biological plausibility.