Abstract Background and Aims Floral colour is a primary signal in plant–pollinator interactions. The association between red flowers and bird pollination is well known, explained by the ‘bee avoidance’ and ‘bird attraction’ hypotheses. Nevertheless, the relative importance of these two hypotheses has rarely been investigated on a large scale, even in terms of colour perception per se. Methods We collected reflectance spectra for 130 red flower species from different continents and ascertained their pollination systems. The spectra were analysed using colour vision models for bees and (three types of) birds, to estimate colour perception by these pollinators. The differences in colour conspicuousness (chromatic and achromatic contrast, purity) and in spectral properties between pollination systems and across continents were analysed. Key Results Compared with other floral colours, red flowers are very conspicuous to birds and much less conspicuous to bees. The red flowers pollinated by bees and by birds are more conspicuous to their respective pollinators. Compared with the bird flowers in the Old World, the New World ones are less conspicuous to bees and may be more conspicuous not only to violet-sensitive but also to ultraviolet-sensitive birds. These differences can be explained by the different properties of the secondary reflectance peak (SP). SP intensity is higher in red flowers pollinated by bees than those pollinated by birds (especially New World bird flowers). A transition from high SP to low SP in red flowers can induce chromatic contrast changes, with a greater effect on reducing attraction to bees than enhancing attraction to birds. Conclusions Shades of red flowers differ between pollination systems. Moreover, red bird flowers are more specialized in the New World than in the Old World. The evolution towards colour specialization is more likely to result in higher efficiency of bee avoidance than bird attraction

中文翻译：

---

红色花朵在授粉系统和各大洲之间的色调有所不同


摘要 背景和目的 花色是植物与传粉媒介相互作用的主要信号。红色花朵和鸟类授粉之间的关联是众所周知的，可以通过“回避蜜蜂”和“吸引鸟类”假设来解释。然而，这两个假设的相对重要性很少被大规模研究，即使就颜色感知本身而言也是如此。方法 我们收集了来自不同大陆的 130 种红花的反射光谱，并确定了它们的授粉系统。使用蜜蜂和（三种）鸟类的色觉模型分析光谱，以估计这些传粉者的颜色感知。分析了授粉系统之间和各大洲之间颜色显着性（彩色和非彩色对比度、纯度）和光谱特性的差异。主要结果 与其他花色相比，红色花朵对于鸟类来说非常显眼，而对于蜜蜂来说则不太显眼。由蜜蜂和鸟类授粉的红色花朵对于它们各自的传粉者来说更加引人注目。与旧大陆的鸟花相比，新大陆的鸟花对蜜蜂来说不太显眼，而且不仅对紫罗兰敏感，而且对紫外线敏感的鸟类也可能更显眼。这些差异可以通过二次反射峰 (SP) 的不同特性来解释。蜜蜂授粉的红色花朵的 SP 强度高于鸟类授粉的红色花朵（尤其是新世界鸟类花朵）。红色花朵从高 SP 到低 SP 的转变会引起色彩对比度的变化，对减少对蜜蜂的吸引力的影响比增强对鸟类的吸引力的影响更大。结论 不同授粉系统的红色花朵的色调不同。 此外，红色鸟花在新世界比在旧世界更加特殊。颜色专业化的进化更有可能导致比吸引鸟类更高的避蜂效率