The Phylogeny of Mutation Rates

Because evolutionary forces act on the entire genome, the key parameter of spontaneous mutation is the mutation rate per genome (or per effective genome, that portion of the genome in which most mutations are deleterious).  Large domains of life display surprisingly common genomic mutation rates, and these may differ among riboviruses, retroviruses, DNA-based microbes, and animals.  In DNA microbes, most genomic rates are about 0.003–0.004 mutations per genome replication, and because genome sizes vary by several orders of magnitude, mutations per average base pair vary reciprocally by the same large factor.  Given the highly diverse life histories of DNA microbes, this constancy is surprising, but recently discovered outliers to this rule have proven informative.  Our knowledge of mutation rates among riboviruses has been constrained by the paucity of well estimated mutation rates and a far smaller range of genome sizes, which have long prevented the recognition of a constant genomic rate, but this situation is beginning to improve.