Gynodioecy is the co-occurrence of females and hermaphrodites in populations. It is usually due to the combined action of cytoplasmic male sterility (CMS) genes and nuclear genes that restore male fertility. According to previous theoretical studies, it is very difficult to explain the maintenance of gynodioecy with CMS and male-fertile cytotypes, although it has been observed in some species. However, only very specific situations have been investigated so far. We present a model to investigate the conditions that promote the maintenance of this breeding system in the case of an outcrossed species when CMS and male-fertile (non-CMS) cytotypes are present in an infinite panmictic population. We show that the type of cost of restoration strongly affects the conditions for stable maintenance of gynodioecy. Stable nuclear-cytoplasmic gynodioecy requires a female advantage, which is a classical condition for gynodioecy, but also a cost of CMS for female fitness, which had been rarely investigated. A cost of restoration is also needed, which could affect either pollen or seeds. Finally, we found that gynodioecy was attainable for a large set of parameter values, including low differences in fitness among genotypes and phenotypes. Our theoretical predictions are compared with previous theoretical work and with results of empirical studies on various gynodioecious species.

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Floral traits that reduce self‐pollination in hermaphroditic plants have usually been interpreted as mechanisms that limit the genetic consequences of self‐fertilization. However, the avoidance of sexual conflict between female and male function (self‐interference) may also represent an important selection pressure for the evolution of floral traits, particularly in self‐incompatible species. Here, we use experimental manipulations to investigate self‐interference in Narcissus assoanus, a self‐incompatible species with a stigma‐height dimorphism in which the degree of spatial separation between sex organs (herkogamy) differs strikingly between the long‐ and short‐styled morphs (hereafter L‐ and S‐morphs). We predicted that weak herkogamy in the L‐morph would cause greater self‐pollination and hence self‐interference. Experimental self‐pollination reduced seed set when it occurred prior to, or simultaneously with, cross‐pollination in the L‐morph, but only if it occurred prior to cross‐pollination in the S‐morph. In the field, autonomous self‐pollination was greater in the L‐morph than the S‐morph, but we found no evidence that self‐interference reduced maternal or paternal fitness in either morph. One‐day‐old flowers of the L‐morph have reduced stigma receptivity and hence exhibit protandry, whereas stigma receptivity and anther dehiscence are concurrent in the S‐morph. This suggests that the two style morphs have alternative strategies for reducing self‐interference: dichogamy in the L‐morph and herkogamy in the S‐morph. These results provide insight into the mechanisms that reduce sexual conflict in hermaphrodite plants and are of significance for understanding the evolution and maintenance of sexual polymorphisms.