The reproductive biology of Melocactus glaucescens and M. paucispinus (Cactaceae) was studied in the municipality of Morro do Chapéu, Chapada Diamantina, Bahia State, comprising the phenology, floral biology, pollination and mating system of the species. It was recorded flowering and fruiting periods, flower visitors, frequency and kind of visits, and the strategy and behavior of the visitors on the flowers. Experimental pollinations were carried out to determine the mating systems of the species. The flowering period of both Melocactus species overlapped during the study period. The floral characteristics of the species are typical of ornithophily: showy colors, tubular structure, and nectar with low concentration of solutes, between 20% and 30%. The hummingbird Chlorostilbon aureoventris Boucier & Mulsant (1948) was the most frequent flower visitor, performing 82% and 89% of the visits in M. paucispinus and M. glaucescens, respectively. Other hummingbird and butterfly species also visited the flowers of both species. The overlap in the flowering period and the similarity in the guild of pollinators of those and other sympatric species of Melocactus favour the occurrence of hybridization, as it has been observed in that area. Melocactus glaucescens presented self-incompatibility and allogamy. Conversely, M. paucispinus is self-compatible and autogamous, however presenting lower fruit set in selfing than in outcrossing, possibly due to the occurrence of inbreeding depression. Interspecific experimental pollinations indicate the occurrence of inter-compatibility between M. paucispinus and M. concinnus Buining & Brederoo, supporting current hypotheses of natural hybridization between them.
Cactaceae; Melocactus; ornithophily; pollination; reproductive biology
