The extent of rapid colour change in male agamid lizards is unrelated to overall sexual dichromatism

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.