Study Species and Sample Collection
We captured three to five sexually mature males (with adult coloration) of each of 27 species of agamid lizards (28 populations, which included genetically differentiated populations of Ctenophorus pictus from Victoria and South Australia, 79 individuals, 186 tissue samples) from various locations in Victoria, South Australia and Western Australia between September 2015 and January 2016 (Figure 1; Table S4). All lizards were sampled during the spring-summer breeding season to record seasonal coloration in some species of the genus Diporiphora . Study species were selected based on the presence or seasonal expression of yellow-red coloration (as described in literature; Cogger 2018; Melville 2019), and to encompass the range of phylogenetic diversity within Australian agamids from a broad geographic and climatic range. Lizards were humanely euthanised with an intraperitoneal injection of sodium pentabarbitone (150 mg/ kg). Skin samples for liquid chromatography-mass spectrometry analysis were biopsied and stored in methanol at -20°C and tubes were wrapped with foil to exclude light. Immediately post-mortem, we took standardized photos from which we extracted RGB values and derived measures of hue, saturation and luminance (full details in Supplementary Information). Although these photos do not capture ultraviolet wavelengths, spectral data show that integument colours of species in this study have very little UV reflectance (Supplementary Information, Figure S4).