The Stock Concept and the Uncoupling of Organismal and Molecular Evolution

Abstract

Evidence in support of the view that molecular evolution proceeds at a steady rate is presented in a brief review. This view of the steady rate of evolution of structural proteins, known as the molecular clock hypothesis, is shown to apply to the kinds of proteins that are commonly examined for variation by means of electrophoretic and immunological techniques in investigations of the stock structure of populations. The review is extended, with examples from the ichthyological literature, to show that the pace of organismal evolution is quite erratic in comparison to the pace of molecular evolution. A resolution of the apparent paradox regarding the uncoupling of the course of molecular and organismal evolution is offered based on the published suggestion of Allan C. Wilson and colleagues that the molecular divergence of any pair of populations should be seen as representing a time scale for the divergence. On this basis, disparities between divergences estimated from molecular and organismal data may be interpreted as reflections of the erratic pace of organismal evolution. Finally, it is suggested that the biological significance of distinctions between populations is to be seen in the summation of the organismal and molecular data.Key words: stock concept, organismal, molecular, evolution