Thermal stability of pigment- and structurally based body coloration in a polymorphic lizard

Animal coloration plays a fundamental role in communication, camouflage, aposematism, mimicry and thermoregulation, and has strong implications for adaptation and diversification. Phenotypic plasticity of color traits can thus affect social, reproductive, antipredator, or thermoregulatory behavior and determining the causes and consequences of color change helps us understand evolution. In contrast to seasonal or ontogenetic color changes, physiological color change in response to fine-scale changes in environmental conditions has received less attention. Temperature-driven, rapid changes in coloration can have profound implications for ecophysiology, particularly in ectotherms. Here, using a widespread color polymorphic lacertid, Podarcis muralis, we study the impact of temperature on the chromatic properties and perception of pigment- and structurally based coloration of different body regions. We subjected male and female adult lizards from different color morphs to two different temperature regimes: cold (25 °C) and hot (≥34 °C) temperature, and quantified color change in the dorsum, belly, throat and ultraviolet (UV)-blue ventrolateral patches using a spectrophotometer. We then applied visual modeling to assess color variation from the perspective of a conspecific and two visual predators. We show that despite minor differences in spectral reflectance metrics, temperature had no significant effect on how color patches are perceived by receivers. Moreover, temperature did not affect existing sex and morph differences in color properties, suggesting that the minor changes we observed have little functional/adaptive consequences in this context. Contrary to results reported in other lizard taxa (iguanians and geckos), our findings suggest that temperature-induced rapid visual color change is unlikely in this lacertid species.