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Dam construction dramatically influences riverine ecosystems, with habitat fragmentation being one of the most serious impacts. This habitat fragmentation is particularly relevant for anadromous species such as salmonids. We examined the effects of habitat fragmentation on masu salmon ( Oncorhynchus masou) populations in Hokkaido, Japan. Specifically, we sampled from 15 locations located above and below a dam region in the Uryu River system, and analyzed the genetic structure of the populations using 10 microsatellite loci. No indication of a significant reduction in genetic diversity, estimated by allelic richness and heterozygosity, was observed within the above-dam region compared to the below-dam region. However, we also found that reducing the number of alleles had occurred within the above-dam region. The analysis of molecular variance and multidimensional scaling analysis indicated significant genetic differentiation between regions and within each region. A significant relationship between genetic and geographic distance was observed in the below-dam region, while no signal of isolation by distance was detected in the above-dam region. This study suggests a possibility of ongoing loss of alleles coinciding with habitat fragmentation caused by anthropogenic environmental changes such as water-level regulation, which negatively impacts genetic structure. [ABSTRACT FROM AUTHOR]

Since some colonies of Argentine ant Linepithema humile were discovered in Japan in 1993, populations of this invasive alien ant species have been expanding their distribution. To resolve the number of invasions and the genetic structure in the early stages of introduction, we inferred the genetic structure and relationships among colonies from eight localities, from analyses of eight nuclear microsatellite DNA markers. F ST analysis, principal component analysis and assignment test showed that at least three highly genetically differentiated groups of Argentine ants are present in Japan. Populations from Hiroshima Bay were grouped together (Hiroshima, Hatsukaichi, Otake, Iwakuni Central and Iwakuni Kuroiso), while those from Kobe and Yanai were both genetically distant from each other and from the Hiroshima Bay group. Hatsukaichi and Kobe are international seaports, suggesting that the by-ship invasion occurred at least twice. The invasion route of the Yanai population is unknown at this moment. The Aichi population was genetically distant from that of the Hiroshima Bay group by the difference in allele frequencies, and it was plausible that the Aichi population was introduced from the Hiroshima Bay group by human-mediated jump dispersal. [ABSTRACT FROM AUTHOR]

At 17 localities in Japan, 71–81% of overwintering adult females of the solitary bee Ceratina flavipes mated before hibernation. The occurrence of males with inseminated females in their natal nests suggested the possible occurrence of inbreeding. Therefore, we examined the seasonal trends of inbreeding coefficients, calculated by comparing the band patterns of microsatellite DNA between a female and her mating partners (indicated by sperm in her spermatheca). The mean coefficient of inbreeding was 0.80 on 25 August and 0.60 on 1 November versus 0.31 on 5 June and 0.38 on 28 June. These results demonstrate a tendency towards inbreeding before winter and towards outbreeding during dispersal after hibernation. [ABSTRACT FROM AUTHOR]

We describe a total of 25 anadromous Sakhalin taimen Hucho perryi collected on the coast of Sarufutsu, northern Hokkaido, Japan in June 1997 and 1999. We examined morphology, stomach contents and growth of three anadromous taimen (one male and two females) in detail, which were preserved in good condition. The three taimen were aged and one female still had some eggs retained in her abdomen. The stomach contents of the three taimen consisted of sand lance Ammodytes personatus Girard and sculpin Triglops sp. On the basis of scale analyses, the growth rate of the three taimen was estimated by using the back-calculation method, and the highest rates were observed at young ages. Guanine pigmentation was present at the base of the caudal fin of each taimen and is considered as a potential morphological trait to differentiate anadromous from fluvial specimens. Another anadromous taimen, of which some individuals had reared for more than 3 years in seawater are also reported. For the conservation of this rare and endangered species, their migration route between rivers and sea should be protected [ABSTRACT FROM AUTHOR]

The habitat usage of a female brown bear, Ursus arctos yesoensis L., was studied in relation to the distribution of food plants in a beech-forest zone of Hokkaido, Japan. The bear’s habitat usage was correlated with the distribution of the plant Angelica ursina (Rupt.) Maxim. in summer. In spring the bear preferred Petasites japonicus (Sieb. et Zucc.) Maxim. and Heracleum dulce Fisch., whose abundance did not differ significantly between Sasa–beech forests and coniferous forests. However, the bear spent more time in coniferous forests where its den site was located. In autumn, this bear preferred the plant Actinidia arguta (Sieb. et Zucc.) Planch. ex Mig., which was abundant in maple–linden forests, however, the bear’s habitat usage was not correlated with the distribution of A. arguta because it frequently returned to an overlapping area where A. arguta was scarce. Thus, the bear’s habitat usage depended on food distribution as well as on the location of the den site and the behavioral core area. [ABSTRACT FROM AUTHOR]

A tardigrade Milnesium tardigradum showed anhydrobiotic capacity, in which the desiccation tolerance, given by the mean survival rate under desiccation at different relative humidity levels, was significantly higher in the Sapporo (Japan) population than that in the Bogor (Indonesia) population. Accordingly, the surviving tardigrades took a significantly longer time for revival in Bogor than those in Sapporo. The higher tolerance of the Sapporo population is thought to be related to the low relative humidity and low temperature such that the animals experience 41% RH in May and often -10 degrees C or lower in winter.