Sexually dichromatic coloration of female Iberian green lizards correlates with health state and reproductive investment

Abstract

Females often have chromatic patterns that differ from those of males. The evolution and function of female coloration is less known than those of males. Female ornaments can result from non-adaptive intersexual genetic correlation, but they may also signal female quality, health state, or potential fecundity. We examined whether the spectral characteristics of the sexually dichromatic coloration of female Iberian green lizards (Lacerta schreiberi) correlate with their condition, parasite load (ticks, hemoparasites and Borrelia infection) and the inflammatory response, and predict reproductive investment and offspring quality. Females with more intense UV-blue throat structural coloration and with more intense carotenoid-dependent yellow chests had less hemoparasites, and females with more saturated green dorsal coloration had lower tick loads. Also, females with greener backs seemed less prone to Borrelia burgdorferi s. l. infection. Surprisingly, in females not infected with Borrelia, there was a negative relationship between tick load and carotenoid content in the chest, which was not obvious in infected females. Characteristics of the females’ coloration may also predict several variables of reproductive investment, such as egg laying date, incubation time, hatchling number, hatching success, and body size and condition of their hatchlings. Because this is a polygynandric species and mating investment is costly for males, we suggest that males might use female coloration to select potential mates. However, we can expect that the physiological basis of coloration is similar in both sexes and, therefore, genetic correlation and sexual selection may act synergistically. Despite widespread misconception that males are brightly colored and females are dull, females of some species also signal their quality with colorful ornaments. However, the function of female coloration is less often studied, although it may be important to fully understand sexual selection. Coloration of female Iberian green lizards is not so bright as that of males, but spectral characteristics of female colors can reflect body condition, parasite load, and immune response and, moreover, predict the number and quality of her future offspring. These correlations might help males to choose among female partners when selecting a good mate is a time and energy demanding task, increasing males’ fitness. This would support direct sexual selection of female ornaments.