| The hypothesis that females could assess heritable quality by analyzing ornaments in sexual selection has been widely discussed. But only a few studies focused on the relationship between morphological characteristics and molecular markers, as well as the tradeoff between the ornaments and the immune system.Golden pheasant (Chrysolophus pictus), a Chinese endemic species, is sexually dimorphic and male ones have longer tails and more gorgeous plumage for courtship display during breeding season, which made it an ideal candidate for mate choice. A large number of golden pheasant distributed in Qinling Mountains, which forms the boundary between Palaearctic realm and Oriental realm of Animal geography in China.Two sets of molecular markers were adopted for our research. One of them were adaptive loci, the major histocompatibility complex (MHC) genes, which are related to parasite resistance and immunocompetence. The other set were neutral ones, microsatellites, which are widely distributed in the eukaryotic genome. These two kinds of molecular markers could reveal the genetic information of population and individuals accurately.We used5MHC loci,2class I and3class II genes and15micro satellite loci to investigate the genetic polymorphism of the FoPing population in Qinling area for golden pheasant. In addition, we compared the distribution of alleles and genotypes between two genders and analyzed the relationship between the morphology, such as the body size and the plumage color, and two markers.The main findings are as follows:First, we used principal component analysis (PCA) to analyze the body size of golden pheasant. The male ones were significantly higher than the females in body length, wing span, wing length, tail length, tarsus length and bill length. Especially, the mean tail length of males was1.8times than that of females. Component t1took over56.50%, which could explain the principal differences between male and female in body sizes. Moreover, the average length of males’golden crest was145mm. Then, we measured the reflectance spectra of orange cape, based on the visual range of birds, and calculated its five parameters:all brightness, R-Y brightness, VIS chroma, hue and UV chroma. The results illustrated the reflectance on the under-side was higher than that on the upper-side at a range of300-700nm. In UV light (300-400nm), the upper-side showed low reflectance, while the under-side plumage displayed a peak. Furthermore, the upper-side exceeded the under-side in following parameters:the VIS chroma and proportion of R-Y brightness in all brightness.The results of micro satellites demonstrated that Foping population of golden pheasant maintained a high level genetic diversity. In addition, the distribution of allele s at SSR loci:CP09, CP10and CP14, were significantly different between genders, and also different between groups with different component t1. However, there was no significant difference of component t1value between homozygotes and heterozygotes. We also haven’t found significant correlation between SSR loci and ornaments like tail size and plumage color.The results of polymorphism at MHC loci showed the rank of mean nucleotide diversity and amino acid polymorphisms both are IIB Exon2>IA exon2>IA exon3. The putative peptide binding sites (PBS) of all MHC loci, except of IA1-E2, were subject to positive selection under different selection pressures.Allele distributions at MHC were different between genders, and we found the proportions of allele01and genotypes0101at IA2-E3in the males were significantly higher than that in the females. The correlation analysis between MHC and body size, plumage color indicated the tail of individuals with homozygous genotypes at IA2-E3and ⅡB1was significantly longer than that of heterozygotes. Furthermore, the tail length of Individuals with0101genotype at ⅡB1was significantly higher than that of other genotypes. As for the all brightness on the upper-side, homozygotes have higher values than heterozygotes at ⅡB1, and individuals with genotype0101or0808have higher values than individuals with other genotypes. Therefore, we found the all brightness on the upper-side was related to MHC class II, but not to MHC class I. Moreover, we haven’t found the correlation between MHC and other morphological characteristics.As a conclusion, the tail length and all brightness of plumage color may be the two main ornaments related with the particular MHC ⅡB1genotypes in males. By evaluating these ornaments, female golden pheasant may acquire the signal of immunity and gene quality, and make the optimal mate choice.Our results confirmed the association of ornaments and MHC class Ⅱ in male golden pheasant and supported the hypothesis of "good gene". We also tried to provide opinions for improving reproduction of golden pheasant. |
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