POPULATION SUBDIVISION AND GENE FLOW IN DANISH HOUSE MICE

Genetic subdivision in local populations of the European house mite, M us musculus domesticus and M. m. musculus, was analysed to study patte rns of gene flow. The data consisted of frequencies of microsatellite alleles in 16 samples (250 individuals) from a total of II sites in Ju tland, which included successive samples from three sites. Sequences o f the control region of mitochondrial DNA in three successive samples from one site were also analysed. Microsatellite genotype frequencies within samples were close to Hardy-Weinberg expectations. Levels of mi crosatellite differentiation among samples (theta = 0.50-0.21) corresp onded to limited gene flow at migration-drift equilibrium (N-m = 1-5). Weak isolation by distance for microsatellites in M. m. musculus sugg ested that gene flow tends to occur among neighbouring sites. Estimate s of effective population size over a few generations were much lower than those corresponding to the long periods needed for arrival at mut ation-drift equilibrium. This suggested that subpopulations had been i nfluenced by gene flow since formation, or had originated recently fro m genetically diverse founders.