FLOWERING SEASONALITY AND FLOWER CHARACTERISTICS OF LORANTHUS-ACACIAEZUCC (LORANTHACEAE) - IMPLICATIONS FOR ADVERTISEMENT AND BIRD-POLLINATION

The flowering biology and pollination ecology of Loranthus acaciae was studied at Hazeva in the northern Arava Valley in Israel. Flowers at anthesis had red anthers, a red stigma and a green corolla which turne d red as a postfloral phenomenon. Their flowering period was approxima tely 10 months long (from mid-June until mid-April) during which time two main flowering patterns were distinguished. Some plants flowered t wice a year, with separate summer and winter flowering periods; other plants flowered continuously, with two peaks, one in the summer and on e in the winter. Several significant differences between summer and wi nter flowering and fruiting were found: (1) the summer flowering perio d was shorter than that of winter, (2) flowering synchrony between ind ividual plants was lower in summer than in winter, (3) in summer the p lants produced a larger proportion of female flowers, whereas in winte r most of the plants produced a larger proportion of hermaphrodites, ( 4) in summer a limited number of plants produced smaller flowers while the majority produced normal-sized flowers, whereas in winter the ent ire population produced only normal-sized flowers, and (5) fruit set p ercentage was lower in summer than in winter. L. acaciae was found to be self-compatible, but, since it was not spontaneously self-pollinate d, it showed high dependence on pollinator activity. In summer the flo wers were visited by a wide spectrum of pollinators, both birds and in sects, while in winter flowers were visited almost exclusively by the orange-tufted sunbird (Nectarinia osea osea, Nectariniidae). These sea sonal changes in flowering characteristics and pollinator activity cou ld explain why reproductive success is higher in winter than in summer .