Data from: MHC variation is related to a sexually selected ornament, survival and parasite resistance in common yellowthroats

Hamilton and Zuk (1982) proposed that females choose mates based on ornaments whose expression is dependent on their genetically based resistance to parasites. The Major Histocompatibility Complex (MHC) plays an important role in pathogen recognition and is a good candidate for testing the relationships between immune genes and both ornament expression and parasite resistance. We tested the hypothesis that female common yellowthroats prefer to mate with more ornamented males, because it is a signal of their MHC-based resistance to parasites and likelihood of survival. In this species, females prefer males that have larger black facial masks as extra-pair mates. Using pyrosequencing, we found that mask size was positively related to the number of different MHC class II alleles, as predicted if greater variation at the MHC allows for the recognition of a greater variety of pathogens. Furthermore, males with more MHC class II alleles had greater apparent survival, and resistance to malaria infection was associated with the presence of a particular MHC class II allele. Thus, extra-pair mating may provide female warblers with immunity genes that are related to parasite resistance, survival and the expression of a male ornament, consistent with good genes models of sexual selection.汉密尔顿与祖克（Hamilton and Zuk，1982）提出，雌性通过装饰性状选择配偶，而该性状的表达依赖于宿主对寄生虫的遗传抗性。主要组织相容性复合体（Major Histocompatibility Complex, MHC）在病原体识别过程中发挥核心作用，是检验免疫基因与装饰性状表达、寄生虫抗性之间关联的理想候选对象。我们验证了如下假说：雌性普通黄喉地莺（common yellowthroat）更倾向于选择装饰性状更显著的雄性作为配偶，因为这类装饰性状是雄性基于MHC的寄生虫抗性与存活潜力的信号。在该物种中，雌性更偏好拥有更大黑色面部面罩的雄性作为婚外配配偶。通过焦磷酸测序（pyrosequencing）技术，我们发现雄性面部面罩的尺寸与MHC II类等位基因的不同数量呈正相关，这与“MHC位点的更大变异可识别更多种类病原体”的预测相符。进一步研究表明，携带更多MHC II类等位基因的雄性表观存活率更高，且对疟原虫感染的抗性与某一特定MHC II类等位基因的存在显著相关。综上，婚外配行为或许能为雌性莺类提供与寄生虫抗性、存活能力及雄性装饰性状表达相关的免疫基因，这与性选择的优质基因模型（good genes models of sexual selection）相一致。