Fig. 2

Comparisons of the reflectance spectra of three varieties of the Rhododendron sanguineum complex. a Reflectance spectra were measured at the midpoint of the corolla tubes of the three varieties. b Three-dimensional plots of the visible spectra that classified by brightness (x-axis), hue (y-axis), and saturation (z-axis) of the three varieties. c Boxplots of brightness values of the reflectance spectra of the three varieties. d Boxplots of the ratios of saturation over hue from reflectance spectra for the three varieties. Boxplots show the median, and the box edges represent the 25th and 75th percentiles of values for a total of 15 individuals for each variety. Statistical significance was determined by a two-tailed Student’s t test. The significant differences are noted as asterisks (*P < 0.05; **P < 0.01; ***P < 0.001). Red represents R. var. sanguineum (RsS); Purple represents R. var. haemaleum (RsH); Yellow represents R. var. didymoides (RsD)