An unexpected case of wind pollination: ambophily in an ornithophilous tropical mountaintop Orobanchaceae

Abstract

Some plant species have a kind of mixed pollination system—ambophily—which rely both on biotic and abiotic (most commonly wind) as pollen vectors. Ambophily remains poorly addressed in the pollination literature and may have been overlooked because existing studies do not quantify the wind contribution in animal-pollinated species. After observing pollen transport by the wind in an Orobanchaceae species with ornithophilous floral phenotype, we hypothesize that this species could be ambophilous. Esterhazya eitenorum Barringer is a (sub-)shrub endemic to a high-altitude grassland (campos de altitude) area in southeastern Brazil. Pollinated mainly by hummingbirds and secondarily by large bees, it presents features generally associated with ornithophily. Bird-pollinated species are not expected to be ambophilous, due to their high resource investment in floral construction and maintenance. However, here we detect ambophily in E. eitenorum by testing the potential for pollen export by the wind as well as seed set after floral visitor exclusion and spontaneous self-pollination treatments, and comparing these with natural conditions. Esterhazya eitenorum has an ambophilous pollination system, with effect size analyses between floral visitor exclusion treatments and natural conditions revealing significant contributions from both abiotic and biotic components. Although its floral phenotype corresponds to the main pollinator, the occurrence of ambophily in E. eitenorum underscores the need for an independent approach to the association of floral phenotypes with pollination vectors, in particular for the detection and better understanding of the evolution of mixed pollination systems.