Polymorphisms for genetic and ecological systems with weak coupling

It is perhaps useful to review various known criteria which may lead to stable polymorphism, and to note that the frequency of the heterozygotes is small while the homozygotes of the different alleles exist in approximately equal proportions.

Abstract

Recent experimental and observational studies have established conclusively that natural populations are often genetically polymorphic at a large proportion of loci. Specifically, the discovery of vast numbers of isozyme polymorphisms for plant, insect and animal organisms (Lewontin and Hubby, 1966; Harris, 1966; Brown and Allard, 1969; Marshall and Allard, 1969; Kojima and Tobari, 1969a, b, and others) provides incontestible evidence of the considerable variability present in wild populations. Moreover, a number of animal populations which appear to be practicing partia1 assortative mating and plant populations which are almost obligate inbreeders, but which do outcross occasionally, exhibit a high degree of polymorphism. A noteworthy fact for many of these highly selfing plant populations where considerable polymorphism is present, is that the frequency of the heterozygotes is small while the homozygotes of the different alleles exist in approximately equal proportions [see Allard, Jain and Workman (1968), Marshall and Allard (1969) and references]. It is perhaps useful to review various known criteria which may lead to stable polymorphism.