New Zealand Journal of Botany abstracts

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Short communication Transoceanic dispersal in the amphiantarctic genus Discaria: an evaluation

JONATHAN A. KEOGH

Portobello Marine Laboratory
University of Otago
P.O. Box 8
Portobello, New Zealand

PETER BANNISTER

Botany Department
University of Otago
P.O. Box 56
Dunedin, New Zealand

Abstract The hypothesis that the presence of Discaria in New Zealand can be attributed to the dispersal of a sea-borne fruit of an ancestral species is examined. It was shown by experiment that all capsules sank after 42 days in seawater, that proportionately more of those that sank early in the experiment had two or more hard seeds, that the germination percentage of seeds that float is considerably less (33%) than those that sink (100%), and that seeds which imbibed full salinity seawater showed a 60% reduction in germinability compared with controls. The nature 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 fruits also mitigate against possible hydrochory of the fruit and the subsequent establishment of an obligately outcrossing ancestor.

Keywords Discaria toumatou; Rhamnaceae; fruit structure; hydrochory; sea-borne dispersal; germ- ination; salinity; New Zealand B93020 Received 2 February 1993; accepted 25 May 1993

B93020 ; Received 2 February 1993; accepted 25 May 1993
New Zealand Journal of Botany, 1993, Vol. 31: 427—430
0028-825X/93/3104-0427 $2.50/0 © The Royal Society of New Zealand 1993

PDF file of entire paper: medium quality (1227K); (scanned from paper original: notes about this process)

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