Abstract
We examined the variation in sexual ornamentation of male Chinese grouse (Tetrastes sewerzowi) in the Gansu Province, China, seeking to identify factors involved in whether ornament size and brightness are honest signals of male quality. Compared to unmated males, mated males had significantly larger and redder combs and, although they did not have significantly larger territories, they defended them more vigorously. Mated males had significantly higher blood carotenoid and testosterone levels, significantly better body condition, and significantly lower parasite loads than unmated males. Our findings are thus consistent with the hypothesis that comb size and color are honest signals of better male quality in the grouse, mediated through lower parasite loads and/or higher testosterone levels.
Highlights
Male ornamentation, such as striking plumage, combs, brightlycolored gapes and wattles are important traits in sexual selection
The color patterns for these traits were not the same and were mainly divided into 2 categories: structural and pigment dependent coloration. In contrast to those produced by pigments, the structural color arises from the physical interaction of light with biological nanostructures and rely on the shape of the material, not its chemical properties, so electron microscope and spectrophotometry are good tools for exploring the surface ultrastructure of selected traits [53]
Pigment dependent coloration relies on molecules that produce colors by the selective absorption and reflection of specific wavelengths of electromagnetic radiation, so reflectance spectrophotometry and digital camera are two common instrumental approaches for measuring the pigment color
Summary
Male ornamentation, such as striking plumage, combs, brightlycolored gapes and wattles are important traits in sexual selection. Colored or exaggerated ornaments are reliable signals for advertising individual quality in both male-male competition and mate choice. Females mating with males having more elaborate ornaments will benefit directly from any or all of: greater paternal investment in young, better habitat quality, lower transmission of parasites, and greater breeding success for their male young [1,2]. Females may assess the variation of male genetic quality by condition dependent traits. Females mating with males having such exaggerated ornaments will gain the indirect benefit of passing the attractive signal to offspring and leaving more descendants. Offspring inherit superior traits for both body condition and vitality from their parents [3,4]
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