Naoki Ohnishi

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.

Development and characterization of polymorphic microsatellite DNA markers for Sasa senanensis (Poaceae: Bambuseae)

Sasa senanensis is a dwarf bamboo species distributed on the floors of cool temperate forests in Japan and adjacent regions. We isolated eight polymorphic microsatellite loci from this species. The number of alleles ranged from two to eight and the observed heterozygosity per locus from 0.13 to 0.74. Seven of the eight loci were also polymorphic in Sasa nipponica. Most of these markers were successfully amplified in other dwarf bamboo species. These markers will be useful for investigating clonal structure and population genetics in some dwarf bamboo species.

Mass-Intrusion-Induced Temporary Shift in the Genetic Structure of an Asian Black Bear Population

Abstract. Some Asian black bears inhabiting Japan are known to invade residential areas, a phenomenon known as mass intrusion. Although mass intrusion occurs in autumn, it can result in genetic mingling. We examined the influence of intrusion on the genetic structure of black bears. Tissue samples were collected from invasive bears in central Japan in the autumn of two mass-intrusion years, 2004 and 2006. We also set hair traps overlapping an area where tissue samples were collected in the summers of 2005, 2006, and 2008. The genotypes of eight microsatellite loci were determined by PCR. Pairwise relatedness (rxy ) was negatively correlated with distance among resident bears, whereas no such relationship was observed among invasive bears. Spatial autocorrelation analysis of the normal bears in 2006 revealed a significantly positive rc value within the 0–65-km-distance class, whereas that of invasive bears in 2006 revealed significantly positive rc values between the 0–15- and 0–65-km-distance classes. We therefore concluded that mass intrusion enabled genetic mingling in autumn leading to alteration of the genetic structure; however, the normal structure subsequently recovered with seasonal movement.

Genetic Characterization of Northernmost Isolated Population of Asian Black Bear (Ursus thibetanus) in Japan

Abstract. The Asian black bear inhabiting the Shimokita Peninsula, the northernmost part of Honshu, Japan, is categorized as one of the endangered local populations (LPs) in the list of threatened species under the Endangered Species Act. The Shimokita population has become geographically isolated and fragmented due to recent human activity. In this study, we conducted DNA sampling between 2005–2007 of two neighboring bear populations across two regions, Shimokita and Tsugaru, and analyzed the genetic characteristics from the mitochondrial control region (approximately 700 bp) and seven microsatellite loci. Based on the analysis of both microsatellite markers and the mitochondrial control region, we found that the genetic diversity of the Shimokita population was lower than that of the Tsugaru population. An assignment test showed that three of 112 individual bears migrated between subpopulations, suggesting the low level of gene flow between subpopulations. The extent of genetic differentiation between populations (Fst) was 0.163 in microsatellites and 0.443 in mtDNA. These findings indicate that the Shimokita population is genetically isolated from other populations by habitat fragmentation due to human activity and historical events.

Isolation and characterization of microsatellite loci in the Amami rabbit (Pentalagus furnessi)

We report on the isolation and characterization of eight polymorphic and five monomorphic microsatellites in the Amami rabbit (Pentalagus furnessi). Microsatellite polymorphism was determined using 25 individuals. There were 2–11 alleles for each polymorphic locus with heterozygosity ranging between 0.08 and 0.76. Linkage disequilibrium was not suggested between any pairs among the eight polymorphic loci. We suggest that these primers be used in future studies to monitor population size, determine dispersal patterns, and genetic diversity within and between populations of this and related species.

Influence of Food Availability on Matrilineal Site Fidelity of Female Asian Black Bears

Abstract. To describe the maintenance process of matrilineal site fidelity in large, solitary mammals, we investigated both the site fidelity over time and the effect of kinship on the space use at a fine (home range) scale under different levels of food availability. We collected location data for female Asian black bears, Ursus thibetanus, using GPS collars and identified microsatellite DNA markers from bears in the Ashio-Nikko Mountains, Japan. We investigated autumn food resources by assessing hard mast productivity. We found high site fidelity over the years from the denning to summer season, and there was spatial proximity among related females (i.e., mother—daughter, grandmother—granddaughter, and sister—sister pairs) from spring to summer and through mid-autumn in moderate/good hard mast years. In autumns of poor hard mast years, although females used sites far from their primary home ranges, they returned to sites near their primary range before den entry. In habitats, where good denning habitat is spatially close to the spring and summer range, maternal communities may range throughout the area during the denning, spring, and summer seasons. When matrilineal site fidelity was suspended during poor mast years, it was reformed by the end of autumn.

Population Genetic Structure of the Asian Black Bear (Ursus thibetanus) within and Across Management Units in Northern Japan

Abstract. We examined the population genetic structure of the Asian black bear (Ursus thibetanus) in a large continuous habitat in northern Japan. To determine how population subdivision relates to management units (MUs) proposed by the Ministry of the Environment, genetic variation in the mitochondrial DNA control region (mtDNA-CR) and seven autosomal microsatellite loci was assessed in bears captured in southern Tohoku. Geographical distribution of the subpopulations was assessed using landscape analyses to find the best-fit model based on maximum entropy (MaxEnt) prediction and cost of movement. Genetic differentiation analyses revealed unique mtDNA-CR haplotypes in the study population. Bayesian population assignment of autosomal loci inferred four genetically distinct subpopulations in the study area (pop 1–4). The main distribution areas of pop1 and pop4 were separated by a high-cost zone for bear movement as a result of land use. Another high-cost zone was identified between pop2 and pop4, while the distribution of pop4 overlapped that of pop3. These results indicate that genetically distinct subpopulations are localized to areas that correspond roughly to MUs. The presence of subpopulations within an MU suggests that each MU is not always a single demographic unit.