The Annual Cycle of Osyris Quadripartita, A Hemiparasitic Dioecious Shrub of Mediterranean Scrublands

Publisher Website
Google Scholar
Abstract
The growth, flowering and fruiting phenology of a southern Spanish population of O. quadripartita (Santalaceae), an evergreen dioecious shrub of Mediterranean habitats, was studied over a 5-yr period. The growth seasons encompasses the period Nov.-Aug. for females and virtually the entire year for males. Males resume growth shortly after the autumn rains, at least 1.5 mo. in advance of females. The mean length of the growing period was significantly longer for males . The flowering period lasts for nearly 6 mo. (March-Sept.) for females and nearly the entire year for males, with a peak in May-June. The flowering peak of males encompassed that of females in all years. The mean length of the flowering period was significantly longer for males. Ripe fruits are produced throughout the year, with a major peak in winter and minor one in spring. The phenological pattern of O. quadripartita seems to be shared only by species from tropical forest or by others that, like itself, are survivors of an old evergreen tropical flora currently living in Mediterranean refugia. Its phenology seems, therefore, not to have experienced substantial variation since the initiation of the Mediterranean climate in the Pliocene. The hemiparasitic habit must have contributed to the persistence, in a strongly seasonal climate, of virtually continuous physiological activity through the year. Sexual differences in phenology are interpreted in terms of the constraints imposed on the organization of the female annual cycle by fruit development and maturation. Males are relieved of this function and allocate the available time among fewer activities. As a result, they exhibit longer average durations of individual functions, greater seasonal spacing of functions, and more flexible integration of activities, than do female plants.