New Zealand Journal of Botany abstracts

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Breeding system and maternal success of a perennial hermaphrodite, Discaria americana (Rhamnaceae)

DIEGO MED AN

Catedra de Botanica
Facultad de Agronomia de la Universidad de
Buenos Aires
Avda. San Martin 4453
ARG-1417 Buenos Aires, Argentina

Abstract Various aspects of the reproductive biology of the perennial hermaphrodite D. americana were studied by combining data from both wild and garden-grown individuals from several years. Reproduction in this species is exclusively sexual and strictly xenogamous, with pollen transfer depending solely on insect vectors. Although flower morphology and phenology do not fully prevent self- pollination, and geitonogamy can easily take place, the level of autogamy was low at fruit initiation and fell later to zero due to abortion of self fruits. Thus, some self-incompatibility mechanism is operative in this species. Only 14% of the flowers initiated fruits, and 7.6% of these produced fully developed capsules. Fruit initiation was pollen-limited at the flower level. Causes of low fruit set could not be unequivocally established but probably include resource limitation. The seed/ovule ratio in fruits bearing viable seeds was 47%, which resulted in a brood size of 1.42. As many sterile fruits completed development as those bearing at least one viable seed. Pre-emergent (maternal) reproductive success (percent ovules becoming viable seeds) was 2.8%. Under near-optimal conditions, post-emergent success (percent viable seeds becoming reproductive individuals) was 24%. Overall fecundity was about 0.7%, representing (for 14-year-old individuals) between 120 and 4800 successful offspring per year.

Keywords Discaria; breeding system; self- incompatibility; reproductive success; seed dis- persal; Rhamnaceae B92028 Received 10 June 1992; accepted 16 April 1993

B92028 ; Received 10 June 1992; accepted 16 April 1993
New Zealand Journal of Botany, 1993, Vol. 31: 175-184
0028-825X/93/3102-0175 $2.50/0 © The Royal Society of New Zealand 1993

PDF file of entire paper: medium quality (1394K); (scanned from paper original: notes about this process)

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