REPRODUCTIVE-BIOLOGY OF THE DISTYLOUS MANETTIA-LUTEO-RUBRA (RUBIACEAE)

The reproductive biology of Manettia luteo-rubra was studied in the co astal montane Atlantic rain forest of southeastern Brazil. This Rubiac eae is a perennial vine that flowers all the year round, but has a flo wering peak during the dry season. It presents reciprocal herkogamy, t hus the plants are morphologically distylous. The morphs occur in a 1: 1 ratio, and pollen diameter and corolla length vary between short and long-styled flowers. Manettia luteo-rubra displays typical heterostyl ous self-incompatibility and sets almost no fruits from self- or intra morph pollinations. The flowers are tubular, red with yellow lobes, an d odourless. Anthesis is asynchronous, and the Bowers last about four days. Concentration of sugars in nectar is similar in both morphs, ca. 24%, this concentration being typical for hummingbird flowers. Three species of hummingbirds are the major pollinators of the flowers of M. luteo-rubra at the study site: the hermits Phaethornis eurynome and P . squalidus, and the trochiline Thalurania glaucopis. Three species of Heliconius butterflies act as minor pollinators. Both morphs of M. lu teo-rubra exhibit natu ral fruit-set of about 80%, this reproductive o utput being maintained throughout the year by the pollinators' constan cy to the flowers.