Data from: Visual modelling suggests a weak relationship between the evolution of ultraviolet vision and plumage colouration in birds

Birds have sophisticated colour vision mediated by four cones types that cover a wide visual spectrum including ultraviolet (UV) wavelengths. Many birds have modest UV-sensitivity provided by violet-sensitive (VS) cones with sensitivity maxima between 400-425 nm. However, some birds have evolved higher UV-sensitivity and a larger visual spectrum given by UV-sensitive (UVS) cones maximally sensitive at 360-370 nm. The reasons for VS-UVS transitions and their relationship to visual ecology remain unclear. It has been hypothesized that the evolution of UVS-cone vision is linked to plumage colours so that visual sensitivity and feather colouration are “matched”. This leads to the specific prediction that UVS-cone vision enhance the discrimination of plumage colours of UVS-birds while such an advantage is absent or less pronounced for VS-bird colouration. We test this hypothesis using knowledge of the complex distribution of UVS-cones among birds combined with mathematical modelling of colour discrimination during different viewing conditions. We find no support for the hypothesis, which, combined with previous studies suggests only a weak relationship between UVS-cone vision and plumage colour evolution. Instead we suggest that UVS-cone vision generally favours colour discrimination, which creates a non-specific selection pressure for the evolution of UVS-cones.鸟类拥有精密的色觉系统，该系统由四种视锥细胞类型介导，可覆盖包括紫外(ultraviolet, UV)波段在内的宽视觉光谱范围。多数鸟类依靠紫敏(violet-sensitive, VS)视锥细胞实现适度的紫外敏感性，这类视锥细胞的敏感峰值位于400~425纳米区间。然而，部分鸟类演化出了更高的紫外敏感性与更宽的视觉光谱，这得益于其紫外敏(UV-sensitive, UVS)视锥细胞——该类细胞的敏感峰值处于360~370纳米区间。视锥细胞类型从VS向UVS的转变原因，及其与视觉生态学的关联，目前仍未明确。已有假说提出，UVS视锥色觉的演化与羽色密切相关，使得视觉敏感性与羽毛着色实现‘匹配’。由此衍生出一项具体预测：UVS视锥色觉可提升UVS型鸟类的羽色辨别能力，而该优势在VS型鸟类的羽色辨别中并不存在，或仅表现得极不显著。本研究结合鸟类UVS视锥细胞的复杂分布规律数据，以及不同观测条件下的羽色辨别数学模型，对该假说进行了检验。研究结果未发现支持该假说的证据，结合既往研究来看，这表明UVS视锥色觉与羽色演化之间仅存在微弱关联。与之相反，本研究提出：UVS视锥色觉整体上有利于色觉辨别，这为UVS视锥细胞的演化带来了非特异性的选择压力。