Is Phillyrea angustifolia L. (Oleaceae) an androdioecious species?

Observations during two or three years on three natural populations of Phillyrea angustifolia growing in contrasting environments in southern France show that two distinct phenotypes occur in approximately equal proportions: hermaphrodites, which produce pollen and seeds, and males, which produce pollen only. The populations studied are thus morphologically androdioecious. Biometric investigation of the two morphs shows that they are clearly distinguished by (1) the shape of the stigma and (2) the ovary which is well developed in hermaphrodites and aborted in males. Neither size of anthers and corolla, nor pollen germination, differ between the two sexes. In the Camargue, where P. angustifolia is presently an invader, controlled crosses between hermaphrodites (selfing and inter-individual) are partially successful. In contrast, such crosses are sterile in the well-established population of the La Gardiole. Hence the Camargue population appears to be functionally androdioecious and La Gardiole functionally dioecious. This breeding system is particularly puzzling, since the occurrence of anemogamy and possible selfing do not fit classical explanations of androdioecy. The ability of hermaphrodites to be functionally male and female could be particularly adaptive in founding populations. Since functional hermaphroditism occurs in expanding populations of the Camargue population, we consider that the androdioecy of P. angustifolia could be a kind of leaky dioecism.