The distylous species of Psychotria conjugens, P. hastisepala e P. sessilis (Rubiaceae) are typical of understory shady. It occurs in the largest fragment (194 ha) of semideciduous forest in Viçosa, Minas Gerais State, southeastern Brazil, where the present study was carried out. The distyly is characterized by the presence of pin (L) and thrum (B) floral morphs in different individual and the dependence on intermorph pollinations (L x B or B x L) of fruit set, is expected to be at balanced proportions (isopleths) of the individuals in the population. The purpose of this study was to determine, for the species mentioned above, the proportion of floral morphs in an area of seven hectares, the dependence on pollinators by testing the intramorph incompatibility (L x L and B x B) by in vivo controlled pollinations; the viability of pollen grains and the existence of grain size dimorphism among floral morphs, and to quantify the production of fruits and seeds per morph. The floral morphs of the species was found in balanced proportions. There was an incompatibility and the viability of pollen grains was high (> 64%). Grains presented dimorphism; the highest diameters were the B. The production of fruits and seeds (one or two) of the morphs of P. sessilis and P. conjugens were similar and in P. hastisepala they were higher in B. In the study area, at the correct conditions, such as habitat, isopleths and the role of pollinator are the factors that seem to promote the reproductive success and therefore the maintenance of local species.
Breeding system; Fruit set; Semideciduous forest
