POPULATION GENETICS OF FARM ANIMALS

Abstract

Statistical analyses on the polymorphisms in the 42 subpopulations of the hybrid goats raised in southwestern islands of Japan were conducted. The polymorphic traits used here were colored or white coat, horned or polled, having or not wattles and supernumerary teats. The purely native goats had already been known to be nearly monomorphic as being colored, horned, wattleless and possessing supernumerary teats, and the Saanen breed introduced there nearly monomorphic as being white and lacking supernumerary teats and polymorphic in having or not both horns and wattles.Geographical cline which was parallel with the grade of urbanization of the locality was observed in the frequency of genes for colored and in the frequency of appearance of supernumerary teats, both of these traits being monomorphic in the immigrants. Degree of genetic differentiation among subpopulations was calculated to be remarkably larger than that obtained in the human subpopulations by Nei and Imaizumi (1966 a and b). These two phenomena would be ascribed, at least partially, to such a peculiarity that the immigration of breeding males is very much influential upon the gene constitution of farm animal populations.The correlation analyses revealed that the completely random combination of genes as not attained and some positive correlation was observed to be remained both within and between subpopulations. Repeated introduction of Saanen breed into each subpopulation and shortage of time to randomize gene combination were considered as the causes of the observed correlations.Effect of selection was also observed in the subpopulations: the polled gene had selective disadvantage and the character of supernumerary teats had selective advantage in comparison with the white coat color gene. The former was explained by the close linkage between the polled gene and the gene for intersexuality.