Floral Biology and Breeding System of Bauhinia benthamiana Taub. (Leguminosae), a Bat-Pollinated Tree in Venezuelan "Llanos"

Abstract

The breeding system and floral characteristics of Bauhinia ungulata L. were investigated during two consecutive flowering cycles (Dec-Feb). This tree grows in savannas in small sized patches scattered in the grassland and in larger tree clusters called “mata.” Anthesis occurs between 17:00 and 19:30. Anther dehiscence and nectar secretion begin one hour after anthesis. Nectar is produced for 10 to 12 hr with an average sugar concentration of 13.5%. Flowers in small trees secrete nectar at a higher rate than do flowers in bigger trees. Two phyllostomatid bat species, Glossophaga soricina and Phyllostomus discolor, visit the flowers of B. ungulata between 20:00 and 4:00. Visits of variable duration occur every 1 to 2 hr. In general, the times of greatest nectar production, of highest solute concentration of the nectar and of most frequent visits by the main pollinators coincide. The flowers are significantly dimorphic in pistil length, and ovules are abortive in the short-pistil flowers. Artificial self- and cross-pollinations in long-and short-pistil flowers show that B. ungulata is genetically self-incompatible and functionally andromonoecious.