Stylar polymorphism on the edge: unusual flower traits in Moroccan Narcissus broussonetii (Amaryllidaceae)

Heterostyly and related polymorphisms (e.g. stigma-height dimorphism) have been used as model systems for studying the origin and maintenance of plant population variability. Stigma-height dimorphism frequently occurs in Narcissus and is associated with a particular flower shape. In the present study, we describe a new, peculiar case of stigma-height dimorphism in Narcissus broussonetii, a species on the margin of the geographical distribution of the genus. We determined the stylar condition of N. broussonetii and its variation across populations, analyzed perianth morphology and its relationship with stylar variation, and compared this species with other stylar dimorphic species of the genus. We also studied the incompatibility system and pollination ecology of the species. Narcissus broussonetii is a style-dimorphic species, as suggested in early studies that were subsequently neglected, and displays unusual flower morphology, with a long floral tube and a virtual absence of a corona. The species shows a late- (ovarian) acting incompatibility system and crosses within and between morphs are fertile. We observed short-tongued diurnal and long-tongued nocturnal pollinators. Our findings confirm that the presence of the observed dimorphism across populations is most probably the result of the joint action of a nonheteromorphic incompatibility system, extremely long and narrow floral tubes, and a combined role of short- and long-tongued pollinators.