A further study of the problem of the maintenance of females in gynodioecious species

Abstract

Models for the maintenance of females in gynodioecious species are reviewed. Some new results are given concerning digenic models and models of cytoplasmic inheritance with restorer genes, when the cytoplasmic and nuclear factors may have fitness effects in addition to their effects on male fertility. It is suggested that many gynodioecious species may be interpreted as having a cytoplasmic-genic inheritance of male-sterility, and that this interpretation would resolve a number of difficulties. However, much of the evidence is circumstantial, and complete details of the genetics are not available for any case of natural polymorphism for male-sterility. This makes it impossible to test the population genetics theories in a more precise way. It is clear, however, that both the digenic and the cytoplasmic- genic model require large fitness differences if a polymorphism for females is to be maintained. Some evidence exists in maize for the type of fitness effect required by the cytoplasmic-genic model. © 1981 The Genetical Society of Great Britain.