The majority of the almost 90% of flowering plants that rely on animals such as bees and butterflies for pollination use bright colourful floral displays to attract their pollinators.
The flowers of Guthriea capensis, the “Hidden Flower”, are just what their common name implies: hidden at ground level, beneath the leaves of the plant and inconspicuous because like the leaves, they are green. However, they are filled with nectar and strongly scented, suggesting that some animal does manage to find and pollinate the “Hidden Flowers”- but which is it?
The answer to this puzzle was recently published in Ecology by researchers from South Africa and The Netherlands, based at UKZN and the Afromontane Research Unit at the University of the Free State. After many fruitless hours of human observation of a population of “Hidden Flowers” in the Maloti-Drakensberg World Heritage Site in South Africa, cameras triggered by motion-detectors finally revealed the identity of a shy and highly surprising pollinator: Drakensberg Crag Lizards, which pick up pollen on their snouts when they visit the flowers to lap nectar. When lizards were experimentally excluded from plants, the number of seeds produced dropped dramatically, by almost 95%. Although flower visitation by lizards is not unknown, it occurs almost exclusively on oceanic islands, and the critical role of lizards for reproduction in Guthriea capensis is virtually unprecedented.
Just how lizards find the “Hidden Flowers” is the next riddle to be solved. Most lizards are insectivorous but, especially in the harsh environments of islands and deserts, and, as this new finding suggests, high mountains, they may develop a sweet tooth and supplement their insect diet with sips of nectar. Lizards can locate food using only odour, and chemical analysis of the scent produced by the “Hidden Flowers” identified compounds which are almost unique in the plant kingdom. It seems likely that these extraordinary scent chemicals are key to attracting the lizard pollinators. Intriguingly, at close range, small orange glands are visible at the base of the inside of the flowers, and these bear a striking resemblance to the orange colour that male lizards develop during the mating season to attract females. This suggests that the flowers may be using a colour that the reptiles recognise to enable them to locate the nectar.
However the lizards find their nectar treats, this study shows that, as indisputably important as insects such as honey bees are for pollination, there are still many unknown and surprising interactions that also need to be conserved if we want to ensure that plants like the mysterious “Hidden Flower” continue to receive visits from the little dragons with a sweet tooth that are critical for the production of seeds for another generation.
Further reading: Cozien RJ, Van der Niet T, Johnson SD, Steenhuisen S-L. Saurian surprise: lizards pollinate South Africa’s enigmatic Hidden Flower. Ecology. Doi: 10.1002/ecy.2670.
Words: Timotheus van Der Niet and Ruth Cozien
Photograph: Ruth Cozien and Steve Johnson