The role of ultraviolet reflectance and pattern in the pollination system of Hypoxis camerooniana

It's the colours you cannot see that are important to the bees of Cameroon.

Ultraviolet light is reflected by approximately 25 % of angiosperm flowers, with the highest reflectance found in plant species with yellow flowers. Many insect pollinators are sensitive to this UV reflectance and this UV vision, together with perception of visible light cues, helps them to distinguish flowers of one species from another. To increase this distinction, some flowers create a pattern of UV reflectance and absorbance on their petals and reproductive organs. These UV patterns are also believed to improve the identification of the landing and/or foraging parts of flowers or mimic such parts to the pollinator. However, the effect of UV signalling on attracting pollinators of particular plant species is still insufficiently studied, especially in the Afrotropics.

A flower of Hypoxis camerooniana under visible light spectrum on the left side and UV spectrum on the right side. It shows the strongly UV absorbing anthers and UV reflecting petals. Image credit: Š. Janeček & J. Mertens.

In a recent study published in AoBP, Klomberg et al. investigated the roles of UV reflectance and patterning and the pollination system of Hypoxis camerooniana, a yellow flowered montane species endemic to the mountains of Nigeria and Cameroon. By manipulating the UV reflectance and pattern of Hypoxis camerooniana in the Afromontane grasslands of Mount Cameroon, the authors have shown how crucial it is for the predominant insect pollinator; bees. Both bees’ preferences for flowers and their behaviour during visits are influenced by changes in UV reflectance. However, the presence of some UV signal is more important than the specific pattern. This is particularly apparent in montane grasslands with higher UV irradiation, where the UV floral colours are important for recognition of the relatively scarce flowers by potential pollinators.

Researcher highlight

Yannick Klomberg was born in the Netherlands, but spent the first years of his life in Africa and afterwards during his studies revisited this continent frequently. Currently he is a PhD student in Ecology with Dr. Štěpán Janeček at the Insect Community Ecology group in the Department of Ecology, Charles University in Prague. His research focuses on the role of floral traits in shaping and predicting plant-pollinator interactions on Mount Cameroon in the understudied Afrotropics.

Yannick is a tropical forest ecologist interested in ecosystem functioning and plant-animal interactions, with a specific focus on African forests and savannas. Furthermore, after having previously worked with large scale botanical data at Naturalis Biodiversity Center (Leiden, The Netherlands) he also became interested in the application of scientific data and tools in shaping conservation efforts.