Figure 2

Receiver-centric variables (chroma) of a tetrahedral color space analysis of blue, fuchsia, Penstemon gentianoides, and P. roseus. (A) red, (B) blue, (C) ultraviolet, (D) green. Plot of variables using a sensory based analysis indicating the location of each point in a tetrahedral color space for avian vision (E) and bi-dimensional for bee vision (F) of blue and fuchsia flowers, with black dots corresponding to individual observations and grey dot represents the mean value. (G) Plot showing chromatic contrasts against the background of fuchsia, blue, P. gentianoides, and P. roseus flowers for hummingbirds (closed circles) and bumblebees (open circles) color perception. Data are color distances (in units of just noticeable differences, JNDs) by color contrast (y-axis) for six contrasts. The dotted horizontal lines indicates JND = 1 (Weber), above which the pair of color contrast is considered to be distinguished by bumblebees and hummingbirds. Points and error bars indicate mean ± standard error chromatic distances between different species and hybrid flower color morphs. *Significance at the 0.05 level, t-test. The plots in figure were generated using ggplot2 in R (https://cran.r-project.org/web/packages/ggplot2/index.html) and edited in Adobe Illustrator CS6 v16.0.0 (Adobe Systems, Inc.).