Genetic and behavioral factors affecting interpopulation color pattern variation in two congeneric chameleon species

We conducted a study on interpopulation variation of color patterns in two congeneric chameleon species, which have an analogous life history. Both species are able to rapidly change color pattern, and context-dependent color patterns often vary across a wide geographic range. Specifically, we tested four hypotheses that can explain the observed interpopulation variation of color patterns by a series of behavioral field trials where the color patterns of individuals were recorded and later analyzed by a deep neural network algorithm. We used redundancy analysis (dbRDA) to relate genetic, spectral, and behavioral predictors to interpopulation color pattern distance. Our results showed that both isolation by distance and alternative mating tactics were significant predictors for interpopulation color pattern variation in Chamaeleo chamaeleon males. In contrast, in C. dilepis, the interpopulation color pattern variation was largely explained by isolation by distance, and the evidence for alternative mating tactics was absent. In both chameleon species, the environmental colors showed no evidence of influencing chameleon interpopulation color pattern variation, regardless of sex or behavioral context. This contrasting finding suggests that interpopulation context-dependent color pattern variations in each species are maintained under a different set of selective pressures or circumstances.

Methods
Image library of the color patterns on the lateral side of Chamaeleo chamaeleon and Chamaeleo dilepis. The white balance of all images was standardized prior to the analysis using the spectral reflectance of the color board (GretagMacBeth ColorChecker chart) and the Photoshop software. Location, sex, body weight and snout-vent length are provided for each specimen in Excel tables. The images are sorted by species, location, and social context (female-female (FF), female-male (MF), and male-male (MM) matches, and single individual on a pole).