The role of nectar production, flower pigments and odour in the pollination of four species of Passiflora (Passifloraceae) in south-eastern Brazil

Abstract

The pollination biology of four species of passionflower was studied in south-eastern Brazil, specifically the importance of chemical features of floral nectar, pigments and odours. All species required pollinators to produce fruits P. alata was pollinated by bees, P. speciosa by hummingbirds, and P. galbana and P. mucronata by bats. Pollinators consumed nectar as a food source. The activity of vertebrate pollinators reflected resource availability: they foraged when large amounts of nectar were available and when quantitative resource predictability was greater. The nectar of the vertebrate-pollinated species was richer in cholesterol and phospholipids, and had a potassium–sodium ratio higher than 1.0. For all species, the light absorption of flowers was paralleled by the pollinators» visual spectral sensitivity. This first report on Passiflora floral volatile compounds showed that there was a greater chemical class diversity among the species pollinated by animals with an acute olfactory sense, such as bees and bats. Benzenoid alcohols were the most represented compounds. The fragrances contained compounds that occur in other plant species and in the exocrine secretions of bees. This study shows a strong association between pollinators and the attracting and rewarding features of flowers.