POPULATION GENETICS OF DOMESTIC EQUIDS

Department of Veterinary Science, University of Kentucky, Lexington, KY 40546-0076 USA

Population genetics is the study of genetic variability in populations and the change in variation in response to various factors. Genetic variability of horse populations has been examined using a number of different types of gene loci. Among these are red cell blood group loci, genes of the major histocompatibility complex, biochemical genetic loci, and DNA microsatellites. Although the loci sampled across a wide number of breeds are biased toward those used in parentage testing, horses show substantial variation within and among breeds. Variability levels of different types of loci do not tend to be highly correlated indicating that different types of genes are telling us different things about the populations. A primary factor that can have an influence upon genetic variation in populations is population size. Levels of genetic variation within horse breeds and feral horse populations are not statictically significantly associated with population size. Also, few horse populations show any evidence of recent bottleneck effects. These results are probably due to the recent isolation of horse breeds and feral populations and to gene flow.