Variations in habitat, season, flower traits and pollinators in dimorphic Narcissus tazetta L. (Amaryllidaceae) in Israel.

Narcissus tazetta shows a genetically-based discrete polymorphism for style length similar to that well known in heterostylous plants. Plants are either short- (S) or long-styled (1). In Israel, marsh populations are dominated by S plants and hill populations by L plants. Populations differ in size, flowering time and duration, flower orientation, inflorescence display, vegetative reproduction, and pollinators. The main visitors to flowers in marshes are hawkmoths, whereas in the hills they are visited by short-tongued insects: solitary bees and hoverflies. The pollination efficiency of these insects was investigated by studying foraging behaviour, visit rate, and pollen deposition on stigmas. Our findings are consistent with the hypothesis of lower efficiency of pollination of S flowers by short-tongued insects, resulting in the exclusion of this morph from the hills. Additionally, we considered the possibility that there might be pollination ecotypes corresponding to the two habitats (marsh and hill) and examined variation in a set of continuous flower traits related to pollination biology. Flower tube length was the only trait showing a distinct difference between the two habitat types. Although the concentration of nectar was not different between habitats, L flowers presented more concentrated nectar than S flowers. Such a difference in nectar concentration may he of adaptive value for the pollination of the L flowers by short-tongued pollinators in the hills.