Differences in conspicuousness between alternative color morphs in a polychromatic lizard

Abstract

In polychromatic species, differences in conspicuousness among alternative color morphs may affect the costs and benefits relating to signal detectability by primary receivers and unintended observers. Using visual modeling, we studied the conspicuousness of the body coloration in a ventrally polychromatic population of common wall lizards (Podarcis muralis). This species shows a complex color pattern that combines brown dorsal coloration, long-wavelength–biased ventral coloration, and ventrolateral ultraviolet (UV)-blue patches that are used to signal male quality. Considering simultaneously the visual system of P. muralis and lizard predators, we quantified the chromatic and achromatic (intensity) contrasts of each body region viewed against natural backgrounds. We also quantified the internal contrast generated by pairs of adjacent color patches on the lizards’ body surface. We found that, in some cases, color patches used for signaling are better tuned to conspecifics than to predators, and are more conspicuous in males than in females. The UV-blue patches viewed against the long-wavelength–biased ventral coloration provide the most conspicuous color combination, suggesting that ventral colors may act as an amplifier and highlighting the relevance of color pattern complexity. In contrast, the dorsal coloration is the most cryptic coloration. The color morphs differ in conspicuousness, probably resulting in differences in signal efficacy as well as in costs caused by predator detection. The orange morph is the most chromatically conspicuous to conspecifics and predators, whereas the white morph shows the least chromatic conspicuousness, suggesting that the trade-off between detection by primary receivers and predators may be morph-dependent.