Nectar properties and the role of sunbirds as pollinators of the golden-flowered tea ().

PREMISE OF THE STUDY

Properties of floral nectar have been used to predict if a plant species is pollinated by birds. To see whether winter-flowering plants evolve nectar properties corresponding to bird pollinators, nectar properties of several species (including the golden-flowered tea), as well as the role of floral visitors as effective pollinators, were examined.

METHODS

Potential pollinators of were identified at different times of day and under various weather conditions. A bird exclusion experiment was used to compare the pollination effectiveness of birds and insects. Nectar sugar components (fructose, glucose, and sucrose) from growing wild and another seven species and 22 additional cultivars (all in cultivation) were examined by high-performance liquid chromatography (HPLC).

KEY RESULTS

The sunbird and honeybees were the most frequent floral visitors to . Honeybee visits were significantly reduced in cloudy/rainy weather. The fruit and seed set of flowers with birds excluded were reduced by 64%, indicating that bird pollination is significant. For the wild populations of , a bagged flower could secrete 157 μL nectar; this nectar has a low sugar concentration (19%) and is sucrose-dominant (87%). The eight species and 22 cultivars had an average sugar concentration of around 30% and a sucrose concentration of 80%, demonstrating sucrose-dominant nectar in species.

CONCLUSIONS

The nectar sugar composition of species was characterized by sucrose dominance. In addition, the large reduction in seed set when birds are excluded in the golden-flowered tea also supports the suggestion that these winter-flowering plants may have evolved with birds as significant pollinators.