Abstract
The validity of the neutral theory of molecular evolution, which holds that almost all allelic substitution during evolution has been due to random genetic drift, is a pivotal question in evolutionary biology. Here it is shown that the theory predicts a 1:1 ratio among isozymes in a species between those which are faster (i.e. have greater anodal mobilities) and those which are slower (i.e. have lesser anodal mobilities) than their homologues in a related species. In fact, observed patterns of isozymic variation display deviations from such a ratio. Significant departures from expected values were found for reptiles, fish and insects. A near significant result was seen for amphibia. The overall deviations are highly significant. The results strongly suggest that a substantial fraction of allozymic substitution has been due to positive Darwinian selection.
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I would like to thank Dr W. F. Ponder for critically reading and commenting on the manuscript.
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Colgan, D. Interspecific isozymic substitution is not random. Heredity 69, 150–159 (1992). https://doi.org/10.1038/hdy.1992.108
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DOI: https://doi.org/10.1038/hdy.1992.108