TRANSOCEANIC DISPERSAL IN THE AMPHIANTARCTIC GENUS DISCARIA - AN EVALUATION

The hypothesis that the presence of Discaria in New Zealand can be att ributed to the dispersal of a sea-borne fruit of an ancestral species is examined. It was shown by experiment that all capsules sank after 4 2 days in seawater, that proportionately more of those that sank early in the experiment had two or more hard seeds, that the germination pe rcentage of seeds that float is considerably less (33%) than those tha t sink (100%), and that seeds which imbibed full salinity seawater sho wed a 60% reduction in germinability compared with controls. The natur e of the fruit, a dry dehiscent capsule, the existence of a foramen in the inner fruit wall, and the preponderance of two or fewer seeded fr uits also mitigate against possible hydrochory of the fruit and the su bsequent establishment of an obligately outcrossing ancestor.