Visual and olfactory floral cues related to ambophilous pollination systems in Poaceae

Abstract

Abstract Usually considered anemophilous, grasses (Poaceae) have been the subject of few studies that recorded insects visiting their flowers. Such visitors, with wind, could act as pollen vectors in a possible ambophilous system. Since colour and scent are floral cues attracting pollinating insects, we aimed to provide the first insights into how these cues could be involved in the attraction of pollinators by grasses. Chloris barbata, Paspalum maritimum (with two morphotypes), P. millegrana and Urochloa plantaginea were studied. We determined the role of each pollen vector (wind and insect) and we registered the frequency of floral visitors. Also, we characterized the colour reflectance of glumes, anthers and stigmas and we determined the colour space in the bee colour hexagon and the chemical composition of floral scents. The floral structures of each species reflect colour differently and are perceived differently by pollinators. Furthermore, the volatile organic compounds detected are similar to those found in entomophilous species. In two of the grass species, we registered eight species of visitors, including bees, wasps and flies. Overall, wind was the most important vector for reproductive success. Insects, however, may induce wind pollination by creating pollen clouds when they visit inflorescences.