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Selected substitutions at one locus can induce stochastic dynamics that resemble genetic drift at a closely linked neutral locus. The pseudohitchhiking model is a one-locus model that approximates these effects and can be used to describe the major consequences of linked selection. As the changes in neutral allele frequencies when hitchhiking are rapid,(More)
Recent efforts to estimate the index of dispersion [R(t)] of molecular evolution-i.e., the ratio of the variance in the number of substitutions on a lineage to the mean number-have suffered from an inability to adjust the data for lineage effects. These effects may include the generation-time dependency of the rate of evolution or improper assumptions about(More)
If the fitnesses of n haploid alleles in a finite population are assigned at random and if the alleles can mutate to one another, and if the population is initially fixed for the kth most fit allele, then the mean number of substitutions that will occur before the most fit allele is fixed is shown to be (formula; see text) when selection is strong and(More)
Genotype-environment interactions may be a potent force maintaining genetic variation in quantitative traits in natural populations. This is shown by a simple model of additive polygenic inheritance in which the additive contributions of alleles vary with the environment. Under simplifying symmetry assumptions, the model implies that the variance of the(More)
  • J H Gillespie
  • 1984
It is argued that the apparent constancy of the rate of molecular evolution may be an artifact due to the very slow rate of evolution of individual amino acids. A statistical analysis of protein evolution using a stationary point process as the null hypothesis leads to the conclusion that molecular evolution is episodic, with short bursts of rapid evolution(More)
This paper concludes that the statistical properties of protein evolution are compatible with a particular model of evolution by natural selection. The argument begins with a statistical description of the molecular clock based on a Poisson process with a randomly varying tick rate. If the time scale of the change of the tick rate of the molecular clock is(More)
The results of a computer simulation study of the role of population size in population genetical models of molecular evolution are presented. If the mutation rate and strength of selection are held fixed and the population size increased, the eight models examined fall into three domains based on their rates of substitution. In the Ohta domain, the rate of(More)
A computer simulation of the process of nucleotide substitutions in a finite haploid population subject to selection in a randomly fluctuating environment provides a number of unexpected results. For rapidly fluctuating environments, substitutions are more regular than random. A small mutation-rate approximation is used to explain the regularity. The(More)