Heterostyly is a floral polymorphism usually associated to intramorph-incompatible mating system. We evaluated reproductive aspects of heterostyly in a Rourea induta Planch. population in a cerrado area of Brasília, Central Brazil. Analyses of the floral biology, breeding systems, fruit set and maturation, seed germination, reproductive phenology and floral visitors of were conducted. The flowers are small (about 11 mm diameter), with single morphology, and have five pistils and two sets of five stamens of unequal lengths. The average lengths of stamens and pistils were significantly different between thrum and pin morphs. However, complete reciprocal herkogamy was not found between stamen and pistil lengths of the two floral morphs. Both morphs are intramorph-incompatible. However, thrums are completely self-incompatible while pins are partially self-compatible. In spite of the differences in the floral morphology and breeding system, the two morphs had similar reproductive success in natural condition. The two floral morphs did not differ significantly in terms of fruit setting and maturation or seed germination rate. Rourea induta produced abundant flowers daily over two short events ("pulsed bang" flowering) and most plants in the population flowered synchronously. Many species of insects, mainly small social bees, were observed visiting the flowers. Our results suggest that partial self-incompatibility, intramorph-incompatibility, and differences between morphs in lengths of stamens and pistils reduced autogamy levels in R. induta. Ultimately, the higher fruit setting by intermorph pollination promotes isoplety and indicates that sexual reproduction in R. induta population depends on pollinators services.
breeding systems; distyly; melittophily; reproductive success; savanna
