Multilocus Systems in Evolution

Abstract

Population studies of genetic variation and microevolution are classically discussed in terms of changes in gene frequencies and the maintenance of polymorphic loci that can be identified by Mendelian analyses. In recent years, however, a great deal of attention has been given to the evolutionary dynamics and polymorphisms of interacting and linked loci (e.g., Clegg et al., 1972; Lewontin, 1974; Karlin, 1976). The special properties of multilocus systems, namely, gene interaction and linkage, were first briefly considered in theory by Fisher (1930) and Wright (1932). Fisher discussed in particular the role of modifiers in the evolution of dominance and clearly recognized the importance of linkage in the evolution of interacting polymorphisms. Wright proposed an intermediate optimum model in which natural selection favors intermediate phenotypes over the extremes for a continuous metric trait and emphasized the role of linkage in the makeup of gametic arrays.