Interpopulation variation in the sexual and pollination systems of two Combretaceae species in Brazilian mangroves

• Sexual system of both species differs among populations in same community.
• Gynodioecy and andromonoecy are novelty to L. racemosa and C. erectus, respectively, compared to other populations.
• Pollination system is generalist for both mangrove species.
• Floral visitor may promote geitonogamy but it can be balanced against cross-fertilization which is favored by plant sexual system.
• Pollinator behavior and reproductive strategies results in high fruit set for both species.

Angiosperms have a broad variety of sexual systems, involving hermaphroditic and unisexual flowers. This variety may be related to the pollination mechanism of each species. Among mangroves, sexual divergence is already known in Laguncularia racemosa C.F. Gaertn., with hermaphroditic and androdioecious populations, and there are records of dioecy for Conocarpus erectus L. However, populations of these species in the northern coast of Pernambuco, Brazil, bear fruits in all individuals, a fact that eliminates the possibility of androdioecy and dioecy. In the present study, we investigated the sexual system of L. racemosa and C. erectus in northern Pernambuco, and assessed its relationship with the pollination system of these species. The population of L. racemosa and C. erectus were gynodioecious and andromonoecious, respectively, which is a novelty. Moreover C. erectus flowers also presenting protogyny. Both species were generalistic, as several insect groups pollinated them. There was a partition of pollinators between these species and reproductive efficiency was high, possibly resulting from the fact that both species are self-compatible and autogamous. However, reproductive success was higher in the presence of pollinators. The pollinators’ foraging behavior, with visits to several flowers of the same individual, could increase geitonogamy, but gynodioecy and andromonoecy associated with protogyny minimize self-pollination, which favors the maintenance of these systems. Our results will give support to future research concerning the evolutionary pathway of sexual diversity among different populations of L. racemosa and C. erectus.