Population size and rate of evolution
It is suggested that in evolution there is much substitution of nearly neutral mutations, for which the selection intensity varies from time to time or from region to region. Since the variance among the selection coefficients of new mutants decreases when the environment becomes uniform, the probability of a mutant being advantageous to the species as a whole increases in more uniform environment (Fig. 1).
Therefore the rate of gene substitution increases in smaller populations, as smaller populations are likely to be distributed over less varied environments.
The adequacy of the model was discussed in relation with the following facts or plausible postulates. 1. A large number of amino acid substitutions during a period corresponding to the formation of new species. 2. Rapid evolution at the phenotypic level of populations having a small size. 3. Many extinctions and expansions of the species in the past.
Key wordsEvolutionary Rate Environmental Diversity Nearly Neutral Mutations Population Size
Unable to display preview. Download preview PDF.
- Crow, J. F.: Proc. 6th Berkeley Symp. Mathematical Statistics and Probability (in press) (1972).Google Scholar
- Fisher, R. A.: The genetical theory of natural selection. Oxford: Clarendon Press 1930.Google Scholar
- Fitch, W. M., Markowitz, E.: Biochem. Genet.4, 579–593 (1970).Google Scholar
- Haldane, J. B. S.: The causes of evolution. New York: Cornell Univ. Press 1932.Google Scholar
- Haldane, J. B. S.: J. Genet.55, 511–524 (1957).Google Scholar
- Kimura, M.: Ann. Math. Stat.28, 882–901 (1957).Google Scholar
- Kimura, M.: Genetics47, 713–719 (1962).Google Scholar
- King, J. L., Jukes, T. H.: Science164, 788–798 (1969).Google Scholar
- Margoliash, E., Barlow, G. H., Byers, V.: Nature (Lond.)288, 723–726 (1970).Google Scholar
- Mayr, E.: Animal species and evolution. Cambridge: The Belknap Press of Harvard Univ. Press 1963.Google Scholar
- Ohno, S.: Evolution by gene duplication. Berlin-Heidelberg-New York: Springer 1970.Google Scholar
- Ohta, T.: Genet. Res.19, 33–38 (1972a).Google Scholar
- Ohta, T.: J. molec. Evolution1, 150–157 (1972b).Google Scholar
- Ohta, T., Kimura, M.: Nature (Lond.)233, 118–119 (1971).Google Scholar
- Simpson, G. G.: Tempo and mode in evolution. New York: Columbia Univ. Press 1944.Google Scholar
- Uzzell, T., Corbin, K. W.: Science172, 1089–1096 (1971).Google Scholar
- Wright, S.: Anat. Rec.44, 287 (1929).Google Scholar
- Wright, S.: Genetics16, 97–159 (1931).Google Scholar
- Wright, S.: J. Genet.30, 257–266 (1935).Google Scholar
- Wright, S.: Amer. Naturalist74, 232–248 (1940).Google Scholar
- Wright, S.: Genetics28, 114–138 (1943).Google Scholar
- Wright, S.: Evolution2, 279–294 (1948).Google Scholar
- Wright, S.: Amer. Naturalist90, 5–24 (1956).Google Scholar