Discovery of distyly in Narcissus (Amaryllidaceae)

There has been disagreement concerning the nature of sexual polymorphisms i n Narcissus, a genus of insect-pollinated geophytes native to the Mediterra nean. The existence of trimorphic heterostyly in the genus has recently bee n confirmed, but the occurrence of distyly remains enigmatic. All sexually dimorphic species previously investigated possess two distinct style length s but anthers of similar height. Stigma-height dimorphism does not qualify as true distyly because of the absence of a reciprocal correspondence in st igma and anther position in the floral morphs. Such reciprocal herkogamy is generally regarded as the defining feature of heterostyly. Here we report on distyly in N. albimarginatus (section Apodanthae), a rare species confin ed to a single mountain in northwestern Morocco. A population composed of e qual numbers of long- and short-styled plants exhibited reciprocal herkogam y with lower anthers of the long-styled morph and upper anthers of the shor t-styled morph corresponding in height to stigmas of short- and long-styled plants, respectively. The presence of both stigma-height dimorphism and di styly in Narcissus is of general significance to theoretical models of the evolution of heterostyly.