ABSTRACT
Dynamic colour change is widespread in ectothermic animals, but has primarily been studied in the context of background matching. For most species, we lack quantitative data on the extent of colour change across different contexts. It is also unclear whether and how colour change varies across body regions, and how overall sexual dichromatism relates to the extent of individual colour change. In this study, we obtained reflectance measures in response to different stimuli for males and females of six species of agamid lizards (Agamidae, sister family to Chameleonidae) comprising three closely related species pairs. We computed the colour volume in a lizard-vision colour space occupied by males and females of each species and estimated overall sexual dichromatism based on the area of non-overlapping male and female colour volumes. As expected, males had larger colour volumes than females, but the extent of colour change in males differed between species and between body regions. Notably, species that were most sexually dichromatic were not necessarily those in which males showed the greatest individual colour change. Our results indicate that the extent of colour change is independent of the degree of sexual dichromatism and demonstrate that colour change on different body regions can vary substantially even between pairs of closely related species.
