Shy flowers attract fewer moths

Last updated: 19 Nov, 2015

Plants with flowers that point upwards may be better at attracting moth pollinators than plants with ‘shy’ flowers that point sideways. A study published in New Phytologist, by researchers in the USA, Germany and South Africa, used two species – Zaluzianskya natalensis and Zaluzianskya microsiphon – to investigate the idea that flower orientation, in combination with floral scent, affects the behaviour of pollinators.

Both flowers are open in the evening and attract hawkmoths, which pollinate them. In the experiment, hawkmoths showed a preference for Z. natalensis flowers. Z. natalensis produces more floral volatiles than Z. microsiphon – it has a stronger ‘scent’ to pollinators – but artificially adding more volatiles to the flowers had no effect on the numbers of hawkmoths that visited. The secret of Z. natalensis’ success doesn’t appear to be its smell.

Extract from Fig. 1 in the article, showing Zaluzianskya natalensis being visited by the hawkmoth Hippotion celerio.

Z. natalensis, however, has flowers that point upward. The researchers found that manipulating the flowers of Z. microsiphon to point upward increased their appeal to hawkmoths, and that manipulating the flowers of Z. natalensis to point downward reduced their appeal. The white portion of the petals was more visible when flowers pointed upward.

"The results show that orientation of flowers can result in reproductive isolation between closely related species," said Dr Diane Campbell, lead author of the study. Reproductive isolation refers to a situation where different species may live in the same area, but their properties prevent them from interbreeding.

This news item is based on the following press release: 'Flowers that Point to the Sky May Attract More Moth Pollinators'.