On the overdispersed molecular clock - PubMed (original) (raw)

On the overdispersed molecular clock

N Takahata. Genetics. 1987 May.

Abstract

Rates of molecular evolution at some loci are more irregular than described by simple Poisson processes. Three situations under which molecular evolution would not follow simple Poisson processes are reevaluated from the viewpoint of the neutrality hypothesis: concomitant or multiple substitutions in a gene, fluctuating substitution rates in time caused by coupled effects of deleterious mutations and bottlenecks, and changes in the degree of selective constraints against a gene (neutral space) caused by successive substitutions. The common underlying assumption that these causes are lineage nonspecific excludes the case where mutation rates themselves change systematically among lineages or taxonomic groups, and severely limits the extent of variation in the number of substitutions among lineages. Even under this stringent condition, however, the third hypothesis, the fluctuating neutral space model, can generate fairly large variation. This is described by a time-dependent renewal process, which does not exhibit any episodic nature of molecular evolution. It is argued that the observed elevated variances in the number of nucleotide or amino acid substitutions do not immediately call for positive Darwinian selection in molecular evolution.

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References

    1. Nature. 1968 Feb 17;217(5129):624-6 - PubMed
    1. Science. 1964 Dec 18;146(3651):1593-4 - PubMed
    1. Science. 1969 May 16;164(3881):788-98 - PubMed
    1. Proc Natl Acad Sci U S A. 1969 Aug;63(4):1181-8 - PubMed
    1. Biochem Genet. 1970 Oct;4(5):579-93 - PubMed

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