Genetic drift, selection and the evolution of the mutation rate

Abstract

As one of the few cellular traits that can be quantified across the tree of life, DNA-replication fidelity provides an excellent platform for understanding fundamental evolutionary processes. Furthermore, because mutation is the ultimate source of all genetic variation, clarifying why mutation rates vary is crucial for understanding all areas of biology. A potentially revealing hypothesis for mutation-rate evolution is that natural selection primarily operates to improve replication fidelity, with the ultimate limits to what can be achieved set by the power of random genetic drift. This drift-barrier hypothesis is consistent with comparative measures of mutation rates, provides a simple explanation for the existence of error-prone polymerases and yields a formal counter-argument to the view that selection fine-tunes gene-specific mutation rates.

Neutral Evolution and Dispersal Limitation Produce Biogeographic Patterns in Microcystis aeruginosa Populations of Lake Systems

“…However, those rates were obtained using fluctuation analyses, which is subject to bias . Also, the values are much higher than that for E. coli, which is inconsistent with the observation that mutation rates are similar for microbes with similar genome sizes (Drake et al, 1998;Lynch et al, 2016). We suspect that the mutation rates may be higher at these resistance loci and do not reflect a genomewide average, which is what is required by the model.…”

“…The mutation rate is based on a literature value for E. coli (m = 5.4E-10 mutations/bp/generation), which should be a good estimate for Microcystis aeruginosa considering the similar genome sizes (E. coli: 4.64E6 bp, Microcystis aeruginosa: 5.84E6 bp) (Drake, Charlesworth, Charlesworth, & Crow, 1998;Lynch et al, 2016) . However, those rates were obtained using fluctuation analyses, which is subject to bias .…”

Disentangling the effects of selection and loss bias on gene dynamics

“…Alternatively or additionally, the observed dependence could emerge if duplication and loss rates per gene decreased with genome size, whereas the HGT rate remains constant. Indeed, an inverse correlation between the genome size and the duplication and loss rates could be expected as long as mutation rates appear to have evolved to lower values in populations with larger N e (41,79).…”

The sources of adaptive variation

“…Adaptation in microbial populations indeed often leads to evolution of mutator strains whose DNA repair is defective, and which produce beneficial mutations more frequently than non-mutators, resulting (often temporarily) in an increased mutation rate [107]. In sexual populations, however, recombination quickly disassociates mutator alleles from any beneficial mutations, and their increased frequency of deleterious mutations favours alleles conferring lower mutation rates [61,108]. The elaborate molecular machinery for correcting errors in DNA replication strongly suggests that natural selection has generally favoured reduced mutation rates [61].…”

“…(b) The evolution of mutation rates, sex and genetic recombination Selection on variants that alter the mutation rate has been intensively studied, both theoretically and experimentally [61,107,108], with the aim of understanding the outcome of the conflict between the potential advantage of producing beneficial mutations, and the fact that most mutations that affect fitness are deleterious [27,61]. In largely asexually reproducing populations, an allele that causes an increased mutation rate (a 'mutator') can remain linked to any beneficial mutations that it induces, and hence increase in frequency by 'hitchhiking' [100].…”