Fundamental theorem of natural selection in two loci

Abstract

Expressions for the various genetic effects in a two locus system are given in terms of the genie and marginal gametic frequencies. The lines of argument leading to an exact expression for the change in mean fitness have been indicated. A set of general conditions is given under which the mean fitness is bound to increase every generation. Two multiplicative loci initially in linkage equilibrium are found to possess this increasing property in addition to two additive loci. The premises in which Fisher's fundamental theorem holds in a two locus system are explored and the results of a recent investigation by Ewens are examined.