Multigenic Selection in Plantago and Drosophila, Two Different Approaches

Abstract

The transformation of Darwin’s original theory of evolution into what is currently known as the neo-Darwinian theory has been accomplished by the insertion and integration of the findings of population genetics and ecology. Especially population genetics theory has contributed substantially to the understanding of the mechanisms of evolution and has provided the tools for a quantitative approach of micro-evolutionary processes. Population genetics models supply the tools for quantitative predictions of the effects of natural selection, genetic drift, gene flow, mutation and non-random mating on the genetic composition of populations. We now know, e.g. that selection is not necessarily only purifying as Darwin thought, but that particular selection mechanisms, like overdominance and some cases of frequency-dependent selection will lead to stable allele frequency equilibria and thus contribute to the maintenance of genetic variation. Population genetics theory has even generated quite revolutionary new ideas with respect to the mechanisms of evolution, as in the neutral theory of molecular evolution. In this theory, so brilliantly summarized in Kimura’s (1983) recent book, the main driving forces in molecular evolution are thought to be mutation and genetic drift, while selection only takes a subordinate position.