Fig. 1. Brightness (A) and hue (C) of males and females are strongly correlated in phylogenetic reduced major axis (RMA) regressions of PC scores (red lines).

Males increased in brightness (r² = 0.74, slope: 1.13, t₇₁₅ = 7.4, P < 0.001) and hue (r² = 0.40, slope: 1.52, t₈₁₆ = 16.9, P < 0.001) at a greater rate than females did (equal rate of change is indicated by the blue dashed line). (B and D) Most evolutionary transitions in brightness (B) and hue (D) were from sexually dichromatic to monochromatic for both males (blue arrows) and females (red arrows). For clarity, arrows are only shown where at least 3% of transitions occurred [median (range) for both PC1 and PC2: 1.0% (0 to 3.7%); n = 72 possible transitions from nine states]. The percentage of evolutionary time in each of the nine states is indicated inside each box. Analysis was based on stochastic character mapping of three categories of brightness and hue for each sex.