Selection in plant populations of effectively infinite size: III. The maintenance of females among hermaphrodites for a biallelic model

Abstract

SUMMARYAn allele or genotype is called protected if for all initial genotype frequencies positive it cannot be lost or does not remain at very low frequencies indefinitely. An analysis of protectedness was made for gynodioecious populations (populations with both female and hermaphrodite individuals) with four different types of one-locus two-allele models for the inheritance of gynodioecy. Ovule and pollen fertilities, together with selfing rates may differ between hermaphrodite genotypes. Such factors have not been considered previously, and lead to new conditions for the maintenance of the sex polymorphism. In particular, the mode of genetic control, and the hermaphrodite ovule and pollen fertilities, together with their selfing rates, may determine whether the female genotype is protected. Differential selfing among hermaphrodites may lead to overdominance and allow the maintenance of the polymorphism, and such differential selfing probably occurs in natural gynodioecious populations. In this connection the significance of models of inbreeding depression was considered.

Gynodioecism inSarcocornia quinqueflora(Salicornieae) in New Zealand

“…The most favourable conditions under which male sterility gene(s) allow the evolution of gynodioecism are likely to be those where a high level of self-fertilisation occurs and there is marked inbreeding depression, and female plants have an increased ovule production (Charlesworth & Charlesworth 1978a). Gregorius et al (1982) emphasise the selfing in hermaphrodites but not the inbreeding depression described by the Charlesworths.…”

“…The evolution of gynodioecism has attracted considerable attentIon since the initial reports of Darwin (1877) and the important paper of Lewis (1941); recent papers include Charlesworth & Charlesworth (1978a, 1978b, Ross (1978Ross ( , 1982, Charlesworth & Ganders (1979), Webb (1979), Lloyd (1980Lloyd ( , 1982, Charlesworth (1981), Gregorius et al (1982Gregorius et al ( , 1983) among others.…”

Gynodioecy in plantago lanceolata L. II Inheritance of three male sterility types

“…Two locus models with various types of gene interaction have been studied by Ross and Shaw (1971). Their conclusion, that male sterility can be maintained by fitness differences between sex phenotypes, irrespective of the number of nuclear genes involved or their mode of interaction, has later been generalised (Lloyd, 1975;Charlesworth, 1981; but see Gregorius et a!., 1982). The mode of genetic control, however, is of importance when overdominance is involved in the inheritance of male sterility (Ross, e.g., 1978).…”

Evolution of reproductive systems in filamentous ascomycetes. II. Evolution of hermaphroditism and other reproductive strategies

“…The evolutionary forces that can account for these different types have been thoroughly studied (Charlesworth & Charlesworth, 1978a, b;Charesworth & Ganders, 1979;Gregorius et al, 1982Gregorius et al, , 1983: for fungi, however, such studies appear to be lacking. This paper is a theoretical analysis of the evolutionary relations between a number of fungal reproductive strategies.…”