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

Abstract

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 developm...