Two sympatric Byrsonima species (Malpighiaceae) differ in phenological and reproductive patterns

Sympatric and taxonomically related species may present pre- and/or postzygotic mechanisms for reproductive isolation. We compared the phenology and reproductive biology of Byrsonima intermedia and B. pachyphylla, two sympatric Malpighiaceae species, growing in a remnant of Cerrado in Central Brazil. Both species are evergreens and do not have an overlapping flowering period. In both species, dispersal occurs during the rainy season with low and intermediate overlap in the production of immature and mature fruits, respectively. Both species exhibit self-incompatibility (SI), or, in the case of B. intermedia, facultative SI, and, hence, depend on pollinators to compensate for the lack of spontaneous self-pollination. The flowers of the Byrsonima species were visited by fifteen species of bees that collected pollen and/or oil. Based on their more appropriate intrafloral posture, Epicharis flava and Centris varia were the main pollinators of both species, presenting more frequent visits and/or exhibiting trapline foraging behavior, tending to promote outcrossing. Temporal variation in flowering period and total or partial self-incompatibility seem to function as prezygotic isolation mechanisms that form barriers to gene flow between the studied species and probably avoid competition among pollinators. Both species make oil and pollen available to flower visitors and pollinators almost the entire year, but since Byrsonima intermedia has a long flowering time and is very abundant in the study area, it seems to be more important in maintaining flower-visiting bees.