Rubiaceae is the largest family with distylous species among the Angiosperms. The distyly in those species may vary in form and degree leading to homostyly, monomorphism and dioecy. The objective of this study was to describe the floral biology, pollination and breeding system of Manettia cordifolia Mart. The study was carried out in The Panga Ecological Station and riverside of the Uberabinha (Uberlândia, MG), and complemented with observations of collections deposited in herbaria. Manettia cordifolia is a vine with flower traits of typical of hummingbird pollination syndrome. The main pollinator was the hummingbird Phaetornis pretrei. The plant cannot be considered a distylous species, although it is in a genera known as distylous. The observed characteristics indicate a species with pin-monomorphy, probably derived from a distylous ancestral. Controlled pollinations showed a self-incompatible and non-apomictic species. Pollen tube growth down to the ovary after selfing is similar to the observed in pin pistils of truly distylous congeneric species. The absence of information on the distyly genetic control in the Rubiaceae makes it difficult to interpret the variations observed on the present study.
distyly; heterostyly; monomorphism; pollination; self-incompatibility
