Spatial genetic relationships in a population of the Japanese wood mouse Apodemus argenteus

Space‐related relationships between individuals were investigated during the breeding season in a natural population of Apodemus argenteus (Temminck) by using the catch‐mark‐release method and microsatellite DNA markers. Several overlapping patterns of home ranges in breeding males and females were observed. Although this species is thought to be monogamous, DNA analysis revealed polygynous mating. In adults, relatedness between sexes was generally low and no apparent spatial genetic structure was observed. In juveniles, however, relatedness and geographical distance be‐tween individuals were significantly negatively correlated. The relatedness between adult females decreased with distance, whereas there was not such a correlation in males. Long‐distance movements were observed in current‐year‐born males. The differences in spatial genetic structure between adults and juveniles are thought to be produced by male‐biased natal dispersal.