Apart from floral morphology and colours perceived by the human eye, ultraviolet (UV) reflectance acts as an important visual advertisement of numerous flowering plant species for pollinators. However, the effect of UV signalling on attracting pollinators of particular plant species is still insufficiently studied, especially in the Afrotropics. Therefore, we studied the pollination system of Hypoxis camerooniana in montane grasslands of Mount Cameroon, West/Central Africa. We focused mainly on the effects of the flowers' UV reflectance on its visitors. We experimentally removed UV reflection from petals either completely or partially. Thereafter, flower visitors were recorded and pistils were collected post-flowering to quantify germinated pollen tubes per treatments. The most important visitors were bees, followed by flies. Due to their contacts with reproductive organs bees are considered as the primary pollinators. Visitation rates were lower when UV reflectance was completely removed, whereas the decrease of frequency on half-treated flowers did not differ significantly from control treatments. The complete removal of UV also affected bees' landing behaviour, but not that of flies. We showed that the presence of UV reflectance is more important than UV pattern for bees visiting flowers of H. camerooniana. We hypothesize that exploiting all flowers irrespective of their pattern can be more efficient for pollinators in the open grasslands of high altitudes to spot these relatively scarce flowers by their UV reflectance. Furthermore, we highlight the necessity of both experimental and natural controls in similar studies to control for additional effects of the used UV manipulations. Many plants advertise their flowers with UV reflectance visible to their insect visitors. By manipulating the UV reflectance and pattern of Hypoxis camerooniana in the Afromontane grasslands of Mount Cameroon, we have shown how crucial it is for the predominant visitor, 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. Especially in montane grasslands with higher UV irradiation, the UV floral colours are important for recognition of flowers by potential pollinators.

中文翻译：

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紫外线反射和图案在拟南芥（Hypoxis camerooniana）（Hypoxidaceae）授粉系统中的作用。

除了人眼可察觉的花卉形态和颜色外，紫外线（UV）反射率还为传粉媒介提供了众多开花植物的重要视觉广告。然而，紫外线信号对吸引特定植物物种的传粉媒介的影响仍未得到充分研究，尤其是在非洲。因此，我们研究了非洲西部/中部非洲喀麦隆山的山地草地上的缺水线虫（Hypoxis camerooniana）的授粉系统。我们主要关注花朵的紫外线反射对其访客的影响。我们通过实验从花瓣上完全或部分去除了UV反射。此后，记录花访者并在开花后收集雌蕊以量化每次处理中发芽的花粉管。最重要的访客是蜜蜂，其次是苍蝇。由于它们与生殖器官接触，蜜蜂被认为是主要的传粉媒介。当完全去除紫外线反射率时，访视率较低，而半处理花的频率降低与对照处理无显着差异。完全去除紫外线也影响蜜蜂的着陆行为，但不影响果蝇的着陆行为。我们表明，对于蜜蜂访问H. camerooniana的花朵，UV反射比UV模式更重要。我们假设，不论花型如何，对所有花朵进行采摘，对于高海拔空旷草地上的授粉者来说，通过其紫外线反射率都能发现这些相对稀少的花朵更为有效。此外，在相似的研究中，我们强调了实验和自然对照的必要性，以控制使用过的紫外线操作的其他效果。许多植物通过昆虫反射者可见的紫外线反射来宣传花朵。通过控制喀麦隆山Afromontane草原上的缺氧骆驼亚目（Hypoxis camerooniana）的紫外线反射率和图案，我们已经证明了它对主要的访客蜜蜂至关重要。蜜蜂对花朵的偏好及其在拜访期间的行为都受到紫外线反射率变化的影响。但是，某些UV信号的存在比特定图案更重要。特别是在紫外线辐射较高的山地草原上，紫外线花色对于潜在的传粉媒介识别花朵非常重要。许多植物通过昆虫反射者可见的紫外线反射来宣传花朵。通过控制喀麦隆山Afromontane草原上的缺氧骆驼亚目（Hypoxis camerooniana）的紫外线反射率和图案，我们已经证明了它对主要的访客蜜蜂至关重要。蜜蜂对花朵的偏好及其在拜访期间的行为都受到紫外线反射率变化的影响。但是，某些UV信号的存在比特定图案更重要。特别是在紫外线辐射较高的山地草原上，紫外线花色对于潜在的传粉媒介识别花朵非常重要。许多植物通过昆虫反射者可见的紫外线反射来宣传花朵。通过控制喀麦隆山Afromontane草原上的缺氧骆驼亚目（Hypoxis camerooniana）的紫外线反射率和图案，我们已经证明了它对主要的访客蜜蜂至关重要。蜜蜂对花朵的偏好及其在拜访期间的行为都受到紫外线反射率变化的影响。但是，某些UV信号的存在比特定图案更重要。特别是在紫外线辐射较高的山地草原上，紫外线花色对于潜在的传粉媒介识别花朵非常重要。蜜蜂对花朵的偏好及其在拜访期间的行为都受到紫外线反射率变化的影响。但是，某些UV信号的存在比特定图案更重要。特别是在紫外线辐射较高的山地草原上，紫外线花色对于潜在的传粉媒介识别花朵非常重要。蜜蜂对花朵的偏好及其在拜访期间的行为都受到紫外线反射率变化的影响。但是，某些UV信号的存在比特定图案更重要。特别是在紫外线辐射较高的山地草原上，紫外线花色对于潜在的传粉媒介识别花朵非常重要。