Beyond Sexual Selection: Natural Selection Related Camouflage and Thermoregulation Shape Sexual Color Dimorphism in <i>Diploderma</i> Lizards

Sexual dimorphism is classically attributed to sexual selection, yet natural selection via sex-specific ecological pressures is equally important. We investigated this interplay by testing how camouflage and thermoregulation shape sexual color dimorphism across four Diploderma lizards with a comparative framework capturing diverse ecologies. Using spectrometry and image analysis, we documented pronounced sexual color dimorphism in dorsal patterns. Females prioritized background matching, while males favored high-contrast surface disruption, except in Diploderma slowinskii where monomorphic strategies suggested habitat-specific adaptations. Male stripes critical for disruption significantly reduced solar heat gain, imposing a physiological cost absent in females. This sex-specific optimization, males sacrificing thermoregulation for camouflage efficacy and females favoring crypsis, demonstrates how divergent natural selection pressures drive sexual color dimorphism evolution. Our findings enhance the understanding of animal coloration beyond the sexual selection paradigm, positioning ecological trade-off as a fundamental mechanism shaping sexual color dimorphism.