POLLINATION AND BREEDING SYSTEM OF 2 COOCCURRING HIRTELLA SPECIES (CHRYSOBALANACEAE) IN CENTRAL BRAZIL

The phenology, major floral characteristics, breeding systems and frui ting success of two co-occurring species of Hirtella: H. glandulosa an d H. gracilipes (Chrysobalanaceae) were studied in Central Brazil. The two species occur as trees in mesophyllous forests but H. glandulosa is frequent also in dense savanna areas. Both species flower at the en d of the dry season (September) and have flowers with one-day longevit y. In both species flowers produce nectar and are pollinated exclusive ly by butterflies. The number of visits recorded and pollination rate in each species were significantly different and indicate that pollina tors prefer H. glandulosa flowers. Natural and controlled fruit sets w ere low in both species. The index of self-incompatibility (ISI) was 0 .17 in H. glandulosa and 0.86 in H. gracilipes. Although ISI in H. gla ndulosa could denote an incompatibility system, the presence of fruits with aborted embryos at different degrees of development point to an inbreeding depression situation. Low pollen viability and fruit set in H. gracilipes suggested reproductive problems which may be linked to hybridization events.