BREEDING SYSTEM AND POLLINATION OF NUPHAR-LUTEUM (L) SMITH (NYMPHAEACEAE) IN NORWAY

Insects visiting Nuphar luteum in southern Norway were caught and identified and their role as pollinators was evaluated by observations of their behaviour. Nuphar luteum is mainly pollinated by Apis mellifera and Bombus spp. Moreover syrphid flies are efficient pollinators. The chrysomelid beetle Donacia crassipes, although sometimes present, plays but a minor role as pollinator. By bagging and emasculating flowers the breeding system was shown to be one of mixed mating. Nuphar luteum is protogynous and primarily cross-pollinated, but because male and female stages overlap during the second day of flowering, and because it is self-compatible, self-fertilization is possible. Agamospermy was not found. In Norway, Nuphar luteum appears to have shifted from a typical beetle pollination syndrome to a non-specific pollination syndrome. Insect - induced autogamy as well as the wide range of pollinators may enhance the species' ability to colonize new lakes.