Floral biology of the distylous Mediterranean shrub Jasminum fruticans (Oleaceae)

Various aspects of the reproductive biology of two populations of the distylous shrub Jasminum fructicans (Oleaceae) in the northwest Iberian Peninsula were studied during 1994 and 1995. This species is a ‘tropical’ relict of pre‐Miocene origin. Two morphs (the L morph with long‐style/short‐pistil, and the S morph with short‐style/ long‐pistil) occur. Our results indicate that morph frequency ratio in the study populations is one‐to‐one. Experimental crosses revealed self‐incompatibility, very weak within‐morph compatibility and strong between‐morph compatibility (in all cases as is typical of distylous species). Pollen grains are larger in S‐morph plants, while both nectar reward and fruit set are higher in L‐morph plants. However, no differences were detected in number of pollen grains per stamen or in pollinator spectrum (the most frequent visitors to flowers of both morphs being species of the hy‐menopteran genera Anthophora, Melecta and Bombus ).