Ultraviolet signaling in sexually dichromatic Andean lizards

Ultraviolet (UV) reflectance is an important yet understudied component of lizard coloration, and its presence and function remain unexplored in the genus Phymaturus. We analyzed the presence and variation of UV reflectance in two closely related and sexually dichromatic species, Phymaturus palluma and Phymaturus roigorum. Spectral reflectance was quantified from 19 body patches across dorsal, lateral, and ventral regions, and conspicuousness was assessed against the natural rocky substrates where these lizards occur. Colorimetric variables (UV brightness, UV chroma, UV hue) were used to evaluate species and sexual differences using generalized mixed models and multivariate analyses. Both species and sexes exhibited UV reflectance, but its magnitude varied strongly among body patches. Ventral and lateral regions showed consistently higher UV reflectance than dorsal ones, suggesting that UV signals are involved in intraspecific communication, since these regions become visible to conspecifics primarily during social encounters. UV hue was the main driver of species and sex differences across patches, while UV brightness differentiated sexes within species and UV chroma contributed disproportionately to interspecific contrasts. These results reveal a multidimensional UV reflectance pattern in Phymaturus and provide a basis for future studies on the role of UV signals in visual communication.