A study is described of the influence of the introduction of a dominant nuclear restorer gene into a cytoplasmic gynodioecious plant population. This study includes the consideration of separate effects on the relative female fertility of nuclear, cytoplasmic and sex (phenotypic) factors. Under these assumptions, the introduction of a dominant nuclear restorer gene into a cytoplasmic gynodioecious population can lead to several different situations: persistence of cytoplasmic gynodioecy, appearance of a nuclear-cytoplasmic gynodioecy, appearance of a nuclear gynodioecy or complete restoration of male fertility. The development of stable nuclear-cytoplasmic gynodioecy in a mathematical model is new and is possible because of the consideration of the separate relative female fertilities. The possibility of a transformation of cytoplasmic gynodioecy into a nuclear one has never been obtained before. It could constitute a route for the appearance of this latter kind of gynodioecy in plant populations. Finally, the possibilities of evolution of gynodioecy from one kind to the other, and towards dioecy, are discussed, as are some theoretical schemes that seem to correspond to observed actual situations.
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