New Zealand Journal of Botany abstracts

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Variation in cypsela morphology in Soliva valdiviana and S. pterosperma (Anthemideae, Asteraceae) in a local population at Auckland, New Zealand

PETER H. LOVELL
CHRISTINE D. MAXWELL*

NINAN JACOBf
Department of Botany
University of Auckland
Private Bag, Auckland, New Zealand

Present address: * Department of Biology, Trent Uni- versity, Peterborough, Ontario, Canada K9J 7B8 t 21 Warwick Court, Bellbird Park, Queensland 4300, Australia Abstract Soliva valdiviana and Soliva ptero- sperma are annual species of Composites, native to South America. They were first recorded in New Zealand about 100 years ago. Soliva taxonomy relies heavily on cypsela shape, although leaf shape has also been used. The shapes of cypselas of S. val- diviana and S. pterosperma are very distinctive and quite different from each other. Collections of cyp- selas from Old Government House grounds, Auck- land showed that, in addition to S. valdiviana and S. pterosperma, a continuum of intermediate- shaped cypselas between the two species was pres- ent. Sometimes a wide range of cypsela shapes could be collected from an area as small as 100 cm2. The variation was not due to differences in cypsela maturity, nor to packaging effects within a capi- tulum. There were only very minor differences in cypsela shape between capitula on the same plant and plants bred true for cypsela shape. Observa- tions on flower and capitulum structures suggest that pollen from the central, tubular flowers which are hermaphrodite but functionally male, is trans- ferred to the receptive stigmas of the peripheral flowers. Although the pollen tube germinates the tube does not penetrate the stigmatic surface. How- ever, in the absence of pollen the cypsela does not develop. It appears that pollination is needed as a trigger for embryo development and that repro- duction is primarily agamospermous. Outcrossing may be uncommon because the bracts enclose the peripheral flowers when they are receptive. The origin of the range of variation of cypsela shape is uncertain. Possibly it arises as a result of occasional outcrossing with predominant agamospermy.

Keywords capitulum; Anthemideae; Astera- ceae; agamospermy; flower; taxonomy

Received 14 February 1986; accepted 8 May 1986
New Zealand Journal of Botany, 1986, Vol. 24: 657-664
0028-825X/86/2404-0657$2.50/0 © Crown copyright 1986

PDF file of entire paper: medium quality (602K); (scanned from paper original: notes about this process)

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