PHENOLOGY AND POLLINATION BIOLOGY OF 5 RANUNCULUS SPECIES IN GIESSEN,CENTRAL GERMANY

Five Ranunculus species, R. acris, R. auricomus, R. bulbosus, R. flamm ula and R. repens were studied in respect to phenology and pollination biology at several places in their natural habitats around Giessen, C entral Germany and at garden-beds of the Giessen University in 1989. P opulation phenology was compared with weather conditions. For R. auric omus, R. bulbosus, and R. acris quite distinct phenology was observed at the two sites, with a much longer flowering period at the bed site. Differences in longevity of individual flowers were observed, even wi thin the same species. In R. acris and R. bulbosus, early and late flo wers of the flowering period lasted more than twice as long as flowers from the middle of the flowering period. In R. flammula this situatio n was inverted. Flower visiting insects, belonging mainly to the Dipte ra, Hymenoptera, and Coleoptera, varied considerably in the natural ha bitats and at the bed sites. Frequency of flower visiting at the natur al sites was highest in R. flammula (45 insects per hour), followed by R. acris (12), and R. bulbosus (8). R. repens has a strong vegetative propagation by runners in addition to generative reproduction, and R. auricomus has asexual (apomictic) reproduction in addition to generat ive reproduction. The two latter species showed a flower visitation fr equency of only 6 and 4 insects per hour, respectively. The great vari ety of flower visiting insects and the substitution of insect species at different sites are an expression of a generalistic pollination syn drome of the studied Ranunculus species.