Tropical forests are notable for their species-rich tree genera, yet how so many similar species coexist in sympatry, despite the potential for pollen flow, is still little understood. Due to their lower relative abundance, rarer congeners are expected to face greater reproductive challenges, including higher hybridization risks and lower pollen receipt. Here we explore how ecological factors relate to pollen flow and pollination success in a group of seven co-flowering monoecious Cola species found at differing relative abundances in the Afrotropical understory. We used network analysis, spatial statistics, and mixed models to relate congeneric and conspecific pollen receipt and pollination success to percent of shared floral visitor taxa, total floral surface area, degree of spatial and temporal proximity, and relative abundance of flowering conspecifics.
Results/Conclusions
Congeneric pollen flow was low relative to conspecific pollen receipt, and not significant for pollination success for most species, despite high connectance between species in terms of both pollen flow and shared floral visitor taxa. Floral surface area, a proxy for the magnitude of the floral signal, was the strongest predictor of pollination success, irrespective of relative abundance of flowering conspecifics, however spatially and temporally isolated individuals received less conspecific pollen than more clustered ones. Based on preliminary data, our results suggest that among the understory Cola species, effective pollination strategies exist to achieve pollination success despite low relative abundance. While further studies are needed, this suggests that, contrary to expectations of a rare species “pollination disadvantage”, pollination strategies and outcomes may contribute positively to species persistence and to the maintenance of biodiversity in tropical forests.