Data from: Roses are red, violets are blue - so how much replication should you do? An assessment of variation in the colour of flowers and birds

After years of qualitative and subjective study, quantitative colour science is now enabling rapid measurement, analysis and comparison of colour traits. However, it has not been determined how many replicates one needs to accurately quantify a species' colours for studies aimed at broad cross-species trait comparison. We address this major methodological knowledge gap. We first quantified and assessed the variance in colour within and between species. Reflectance spectra of flowers from ten plant species and plumage of 20 bird species were measured using a spectrometer, and reflectance (i.e. brightness) and tetrahedral colour-space coordinates were calculated. analysis of variance (ANOVA) analyses indicate that there is far more variation in the colours of birds and flowers between species (> 77%) than within species. A Mean Absolute Deviation from the Mean test was applied to indicate the sampling replication required for each species. Tetrahedral coordinates were sampled precisely with only one individual per species. Greater replication was needed to sample reflectance with the desired precision, particularly for darker coloured species. Our findings will allow researchers to allocate their sampling effort in a way that maximises the precision of their colour data collection. The fact that only a few replicates per species are necessary will greatly facilitate broad cross-species comparisons of colour in the future.经过多年的定性与主观性研究，定量色彩科学（quantitative colour science）如今已可实现色彩性状的快速测量、分析与比较。然而，目前尚未明确：若要开展面向广谱跨物种色彩性状比较的研究，究竟需要多少次重复采样才能精准量化某一物种的色彩特征。我们针对这一重大方法学知识空白展开了相关研究。我们首先对物种内部与物种间的色彩变异进行了量化与评估：采用光谱仪（spectrometer）测量了10种植物的花朵反射光谱与20种鸟类的羽毛反射光谱，并计算了反射率（即亮度）与四面体色彩空间（tetrahedral colour-space）坐标。方差分析（analysis of variance, ANOVA）结果显示，鸟类与花卉的色彩在物种间的变异占比（>77%）远高于物种内部。随后，我们采用均值绝对偏差（Mean Absolute Deviation from the Mean）检验，以确定各物种所需的采样重复次数：结果表明，仅需每个物种1个个体即可精准采样四面体色彩空间坐标；若要以预设精度获取反射率数据，则需要更多的重复采样，对于色彩较深的物种而言尤为如此。本研究结果可帮助研究人员合理分配采样精力，以最大化色彩数据采集的精度；而每个物种仅需少量重复采样这一结论，也将极大推动未来跨物种色彩比较研究的开展。