Gynodioecy (coexistence of females and hermaphrodites) is a sexual system that occurs in numerous flowering plants, so understanding the features that affect its maintenance has wide importance. Models predict that females must have a seed fitness advantage over hermaphrodites, and this may be achieved via seed quality or quantity. Females in a population of Fragaria vesca subsp. bracteata, a long-lived gynodioecious perennial, do not demonstrate a seed quantity advantage, so a recent study in Annals of Botany explored whether females produced better quality seed via maternal sex effects or avoidance of inbreeding depression (IBD).
The results show that the offspring of females were more likely to germinate in benign conditions and survive in harsh resource environments than outbred progeny of hermaphrodites. IBD was low across most life stages, and both the effect of maternal sex on progeny quality and the expression of IBD depended on both maternal family and resource condition of the progeny.
In this study, the effect of maternal sex and IBD on progeny quality depended on resource conditions, maternal lineage and progeny life stage. In conjunction with known lack of differences in seed quantity, the quality advantages and IBD observed here are still unlikely to be sufficient for maintenance of gynodioecy under nuclear inheritance of male sterility. This means that additional research needs to be conducted before we can draw final conclusions regarding the mechanisms by which females are maintained in many plant species.