FRUIT-SET, FRUIT REDUCTION, AND FRUITING STRATEGY IN CORNUS-SANGUINEA(CORNACEAE)

We studied various aspects of the fruiting biology of Cornus sanguinea (Cornaceae), a fleshy-fruit-producing deciduous shrub, in four popula tions in northwest Spain. One population was studied over a 5-yr perio d (1989-1994), and the remaining populations in 1994 only. Fruit-set l evel varied among years (range 11-18%) and among populations (range 8- 22%), but was in all cases low. Within plants, fruit-set level did not vary significantly among inflorescences, indicating that inflorescenc e fruit set is independent of inflorescence position and inflorescence phenology. To investigate the function of surplus Bowers, we carried out. flower removal experiments. Inflorescence fruit-set level was una ffected by removal of up to approximate to 75% of flowers. These resul ts suggest that Cornus sanguinea regulates its fruit-set level via pla sticity in the number of fruits aborted: if flower mortality has been high, fewer fruits will be aborted. Within the inflorescence, surplus flowers thus act as insurance against flower loss.