MATE CHOICE, MALE CONDITION-DEPENDENT ORNAMENTATION AND MHC IN THE PHEASANT

The Hamilton and Zuk model predicts that genes for resistance to vario us pathogens may be continuously heritable due to selection disequilib ria caused by coadaptional cycles of hosts and pathogens. The model fu rther suggests that the expression of male secondary ornaments is cond ition-dependent and that only individuals with superior genetic diseas e resistance and vigour can fully express exaggerated secondary orname nts. Female choice is therefore expected to discriminate among males o n the basis of secondary sexual characters in order to pass on genes f or disease resistance that improve fitness in the offspring. In wild r ing-necked pheasants, Phasianus colchicus, of the Revinge area in sout hern Sweden, females prefer to mate with long-spurred males and data o n reproductive success indicate that they may improve their chicks' su rvival rate by doing so. Male spur length is positively correlated wit h age, body size and viability. MHC genotyping for both class I and cl ass II B of pheasant males trapped in the study area identified eight MHC haplotypes and a total of 17 different MHC genotypes. Multivariate analyses revealed that MHC genotype is significantly associated with variation in both male spur length and male viability. These data indi cate that polymorphic genes with a central role in immune recognition can be associated with viability and the expression of a condition-dep endent intersexually selected male trait, thus supporting essential pa rts of the Hamilton and Zuk model.