Seasonal changes in color patches and parasite load of male torquate lizards ( Sceloporus torquatus )

The parasite-mediated sexual selection hypothesis predicts that color expression in color patches of animals can honestly reflect male quality in terms of resistance to parasites. Sceloporine lizards have structural-based blue color patches that can act as intraspecific signals and may thus reflect immunocompetence. However, both color patch expression and intensity of parasitic infections in lizards can vary across seasons. In consequence, we might expect that coloration would honestly reflect immunocompetence to resist parasites only during the mating season. We sampled males of Sceloporus torquatus in central Mexico in spring, summer, and autumn and quantified the reflectance of two structural-based color patches (throat and venter), abundance of two categories of parasites (mites and hemoparasites), and lizards’ local inflammatory response to a mitogen (IRM) as a measure of immunocompetence. We examined whether (i) the coloration of lizards changed across seasons in the population, (ii) there is a relationship between coloration and parasite load and/or IRM, and (iii) the latter relationships remained consistent across seasons. Our study shows that color expression seasonally varied; the structural-based coloration of the two patches was significantly more intense in summer, before the mating season. Furthermore, the throat color was more intense in those males with lower parasite load and higher IRM. However, season had no effect on these relationships, suggesting that color expression in the males of S. torquatus can consistently reflect some components of their immunocompetence throughout the year, supporting the honesty of the structural-based coloration in this species. Significance statement In this study, we aimed to investigate the seasonal variation in structural coloration of a lizard species and its potential relationship with male quality in Torquate lizards (Sceloporus torquatus). Our results revealed distinct seasonal differences in color expression, and furthermore, we found that males displaying more intense blue coloration exhibited lower parasite loads and stronger immune responses. These findings contribute to our understanding of two key aspects: (i) the potential role of structural coloration as an honest signal in organisms of this nature, and (ii) the significance of considering sampling times in organisms with structural coloration, as it can vary throughout the year.