Reproductive biology of Palicourea macrobotrys Ruiz & Pavon (Rubiaceae): a possible case of homostyly in the genus Palicourea Aubl.

The genus Palicourea Aubl. (Rubiaceae) is restricted to the neotropics and includes approximately 200 species of shrubs and small trees. Flowers are mostly distylous, colored, odorless and tubular in cymose inflorescences and usually pollinated by hummingbirds. Homostyly is a rare condition in the genus. The objective of this study is to characterize the reproductive biology of Palicourea macrobotrys Ruiz & Pavon, the pollination biology and identifying the breeding system. The study was carried out in the Panga Ecological Station, Uberlândia, MG (19°11'10" S and 48°24'35" W), from May 2000 to May 2001. The species bloomed from December to June, and fruits were produced in March. It presented inflorescences with ca. 60 hermaphrodite, pentamerous, isostemous and homostylous flowers. Flowers opened between 5:00 and 7:00 h and last 14 hours. Nectar production was small (6.86 µL) with a mean concentration of sugars of 18%. The floral visitors were ants, small bees, butterflies and hummingbirds, which were active mainly in the morning, between 7:00 and 12:00 h. The hummingbird Thalurania furcata was considered the main pollinator due to its visiting behavior and frequency of visits. The species is self-compatible, and the pollen tubes reached the ovary four hours after self and cross pollinations.

homostyly; Palicourea; pollination; reproductive biology; Rubiaceae