Study Species and Sample Collection
We captured three to five individuals 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 S6). All individuals were adult males
for all but one species, Ctenophorus maculosus , for which we
sampled a female because it is the only species in our dataset with
reverse sexual dichromatism. 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) after the lizard was calm in cloth bag and within 48 hours
of capture. 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). Additionally, lizard
colours derived from RGB have been shown to have a statistically similar
distribution to near-simultaneously collected spectral data mapped in
avian and agamid lizard visual color space (Smith et al. 2016).
We took skin samples for liquid chromatography-mass spectrometry (LC-MS)
analysis and stored the samples in methanol at -20°C in foil-wrapped
tubes.