Floral biology and breeding system of Bauhinia forficata (Leguminosae: Caesalpinioideae), a moth-pollinated tree in southeastern Brazil

Abstract

Floral biology and breeding system of Bauhinia forficata (Leguminosae: Caesalpinioideae), a moth-pollinated tree in southeastern Brazil. Bauhinia trees have a wide variety of pollination and breeding systems that are affected by geographic distribution. Bauhinia species with nocturnal anthesis are usually chiropterophilous and/or sphingophilous. B. forficata Link has floral features that are typical of the sphingophilous condition and this report describes the floral biology, pollination, and breeding system of a population of this species in a small fragment of semideciduous forest in southeastern Brazil. Flowers lasted 18 h, anthesis started at dusk, and pollen release and nectar production occurred at 8:00 and 10:00 pm, respectively. Flowers were protandrous and the stigma became receptive around 11:00 pm with the bisexual phase ending at 12:00 am. Nectar was produced continuously; the mean total nectar volume/flower was 15.11 μL and the mean total nectar concentration was 25.9 %. B. forficata is a strictly sphingophilous species that is pollinated exclusively by Manduca sexta L., the body morphology and behavior of which favor pollen transfer. Visitation by the bees Eulaema nigrita Lepeletier and Xylocopa brasilianorum L. (Apidae) occurred in the morning, but these species were considered occasional and not legitimate pollinators. Despite the geographic distance separating the Brazilian B. forficata from the Venezuelan B. aculeata, both species show very convergent pollination systems but differs in their faunal composition. B. forficata is homomorphic and predominantly self-incompatible; cross-pollination produces twice as much fruit as natural open pollinations, indicating a pollen limitation and relative inefficiency of the pollinator, the latter effect may reflect habitat disturbance that favors geitonogamous pollination and decreases the efficiency of pollination. More studies are necessary to investigate the relationship between habitat disturbance and geographic distribution on the pollination and breeding systems of Bauhinia species.