Western Honshu Research Articles

Aseismic deep subduction of the Philippine Sea plate and slab window

We have made great efforts to collect and combine a large number of high-quality data from local earthquakes and teleseismic events recorded by the dense seismic networks in both South Korea and West Japan. This is the first time that a large number of Korean and Japanese seismic data sets are analyzed jointly. As a result, a high-resolution 3-D P-wave velocity model down to 700-km depth is determined, which clearly shows that the Philippine Sea (PHS) plate has subducted aseismically down to ∼460km depth under the Japan Sea, Tsushima Strait and East China Sea. The aseismic PHS slab is visible in two areas: one is under the Japan Sea off western Honshu, and the other is under East China Sea off western Kyushu. However, the aseismic PHS slab is not visible between the two areas, where a slab window has formed. The slab window is located beneath the center of the present study region where many teleseismic rays crisscross. Detailed synthetic tests were conducted, which indicate that both the aseismic PHS slab and the slab window are robust features. Using the teleseismic data recorded by the Japanese stations alone, the aseismic PHS slab and the slab window were also revealed (Zhao et al., 2012), though the ray paths in the Japanese data set crisscross less well offshore. The slab window may be caused by the subducted Kyushu-Palau Ridge and Kinan Seamount Chain where the PHS slab may be segmented. Hot mantle upwelling is revealed in the big mantle wedge above the Pacific slab under the present study region, which may have facilitated the formation of the PHS slab window. These novel findings may shed new light on the subduction history of the PHS plate and the dynamic evolution of the Japan subduction zone.

Evaluation of Camera-Trap Designs for Photographing Chest Marks of the Free-Ranging Asiatic Black Bear,Ursus thibetanus

Estimating animal numbers in the wild is important for decisive conservation and management. However, it is difficult to perform, especially for rare or elusive species because it often requires assumption and high costs, and it is also labor intensive. The Asiatic black bear (Ursus thibetanus), distributed in southern and eastern Asia, is threatened in much of its native habitat and is designated as “vulnerable” according to the IUCN Red List (Garshelis and Steinmetz 2008). In Japan, the bear is divided into 19 local populations based on habitat continuity (Yoneda 2001). The population in Kyushu is probably extinct, and five populations located mainly in western Honshu are considered threatened (Ministry of the Environment 2002). On the other hand, conflicts with humans, such as crop damage, and injury to humans have recently increased in most local bear populations in Japan because of changes or expansion in bear distribution (Oi and Yamazaki 2006). These events have led to heavy culling to prevent nuisance behavior, but the effect of such operations on population viability is becoming a cause for concern. Therefore, accurate evaluation of the current status of each local population is essential for conservation and management. In recent years, the mark-recapture model has been applied using a DNA fingerprinting method (genetic tagging) based on genetic material obtained from collected bear hair (Woods et al. 1999; Mowat and Strobeck 2000). Development of this investigation method known as a “hair-trap” appears to be effective for estimating bear populations, which has been an almost impossible task in the past. However, it has been reported that the method may have a potential weakness associated with high genotyping error rates due to the low quantity and quality of DNA (Gagneux et al. 1997; Goossens et al. 1998). In addition, the high cost of DNA analysis limits extensive and consistent monitoring. Consequently, we paid attention to the “camera-trap” method, which is relatively simple, cost effective, and easy to perform. It also has great advantages in field studies for animal conservation and management. Recently, this method that identifies individuals based on natural markings such as coat patterns from photographs has been used frequently for estimating mainly felid populations (e.g., Foster and Harmsen 2011; O’Connell et al. 2011). The Asiatic black bear is well known to have a crescent-shaped chest mark which is considered to be unique to each bear (Higashide et al. 2012). In other words, if chest marks can be photographed by a cameratrap, this method will be applicable for estimating bear populations and for researching other ecological topics. However, the chest mark is difficult to photograph, because it is not very visible while the bear is walking, in contrast to many other animals which have natural marks over their whole body. Although Ngoprasert et al. (2010) managed to photograph some chest marks in their preliminary study, their results were unsuccessful. Consequently, it is necessary to develop a practical camera-trap technique for effectively photographing chest marks. In addition, a method must be devised for inducing a bear into a posture that enables their chest mark to be clearly photographed. We devised two types of camera-trap as part of a study to identify individual Asiatic black bears by natural markings as a prelude to estimating population size. This paper describes the design of the traps and assesses their utility. It also evaluates the photography success rate and photographic quality.

Population Dynamics and Long-term Survival of Hilgendorf's Tube-Nosed batMurina hilgendorfiin the Akiyoshi-Dai Karst Area, Yamaguchi, Japan

Hilgendorf’s tube-nosed bat, Murina hilgendorfi (Vespertilionidae) is distributed throughout northern China, along the upper Yenisei River in Mongolia and Russia, in the Altai Mountains of Central Asia, in the Primorye Territory, on Sakhalin Island in Russia, and in Korea and Japan (Kawai 2009). In Japan, only one or a few individuals are typically observed at roosting sites (Kawai 2009). Interestingly, only two roosting sites found in July 1958 and 2006 have been confirmed as nursery roosts of M. hilgendorfi (Kuroko 1958; Sato and Katsuta 2007); a tree canopy on Mt Hiko in Kyushu and a tunnel in the vicinity of the Tenryu River in central Honshu. According to recent reports of seasonal fluctuations in the population of this species in Shiga and Osaka prefectures (Abe and Maeda 2004; Harada 2011; Urano 2011), the bats congregate in caves or a shelter from November to the following June, but the bats are generally absent from these roosting sites from July to October, although a few individuals have occasionally been observed at the roosting sites during this time. Our previous banding surveys revealed that M. hilgendorfi roosts in several caves in the Akiyoshi-dai karst area of Yamaguchi Prefecture in Western Honshu from January until June (Matsumura et al. 2005), and that the number of individuals in the caves increases during April and May (Matsumura et al. 2005; Hashimoto and Matsumura 2008). Before these surveys, bat banding studies on M. hilgendorfi population dynamics had been conducted in caves in the Akiyoshi-dai karst area from 1972 to 1997 (Kuramoto et al. 1975, 1998). However, despite the long-term nature of those surveys, no nursery colonies were found in the caves of the areas surveyed. In addition, no direct evidence of the reproductive status of the few bats that were found in the caves from early spring to late summer was reported (Kuramoto et al. 1998). Although several reports have recently been published on the seasonal changes in cave usage as an ecological trait of M. hilgendorfi (Abe and Maeda 2004; Harada 2011; Urano 2011), no studies have specifically examined the life span of this species. To clarify the population dynamics of M. hilgendorfi in the caves of the Akiyoshi-dai karst area, we therefore examined the long-term movements of these bats from March 2002 to April 2011 using bat banding.

A New Oxyurid Species (Nematoda) Collected from a Japanese Serow,Capricornis crispus(Mammalia: Bovidae), in Japan

Skrjabinema kamosika sp. n. (Nematoda: Oxyuridae) is described based on both sexes collected from endemic Japanese serows, Capricornis crispus (Mammalia: Bovidae), of Wakayama Prefecture, western Honshu Island, and Kochi Prefecture, Shikoku Island, Japan. It is readily distinguished from the congeners by having tricuspid sub-interlabial projections in males, large triangular lateral lobes of the lips that do not reach the mouth rim, and a large length ratio of alate/nonalate portions of the tail in females. Close identity in the nucleotide arrangement of ITS2 region between the present material and that from C. crispus of Iwate Prefecture, northern Honshu Island, suggests wide distribution of S. kamosika in Japan. In partial 18S rDNA nucleotide sequence, 0.77% differed from that of Skrjabinema sp. from Capra hircus in the United States.

A New Species of theFejervarya limnocharisComplex from Japan (Anura, Dicroglossidae)

We describe a new species of dicroglossid frog of the Fejervarya limnocharis complex from western Honshu, Japan Mainland. The new species, Fejervarya kawamurai, is genetically closer to F. sakishimensis than to F. limnocharis. It differs from F. sakishimensis by smaller tympanum, head, forelimb, hindlimb, foot, and tibia lengths, all relative to snout-vent length, and from F. multistriata by relatively shorter forelimb, hindlimb, foot, and tibia. From F. limnocharis and F. iskandari, it is differentiated by relatively smaller forelimb, hindlimb, foot, and tibia lengths. Taxonomic problems of Fejervarya populations occurring in Central Ryukyus, continental China, and Taiwan are discussed.

Phylogeography of Japanese Population ofPhelotrupes auratus(Coleoptera, Geotrupidae) Inferred from Mitochondrial DNA Sequences

A partial sequence of the mitochondrial cytochrome c oxidase subunit I (COI) gene (745 bp) was determined for 57 specimens of a geotrupid beetle (Phelotrupes auratus) from throughout the Japanese archipelago. Of the 57 beetles examined, 42 haplotypes were identified. Phylogenetic trees inferred using maximum parsimony, neighbor joining, and Bayesian inference methods were highly congruent. Reconstructed phylogenetic relationships indicated that P. auratus from the Japanese archipelago was separated into two distinct lineages: Group A, which consisted of 35 haplotypes from Honshu, Shikoku, and Hokkaido Islands, and Group B, which consisted of seven haplotypes from Kyushu and Yakushima Islands. In addition, two sublineages were also recognized within Group A: Subgroup A-1, which consisted of 11 haplotypes from eastern Honshu and Hokkaido, and Subgroup A-2, which consisted of 10 haplotypes from western Honshu and Shikoku. Average genetic distances within Group A were positively correlated to geographic distance between sampling localities. Phylogenetic relationships among haplotypes did not correspond to subspecies classification.

Late Pliocene alluvial fan-braided river facies The Doigahama Formation in western Honshu

Late Pliocene alluvial fan-braided river facies The Doigahama Formation in western Honshu

Revised age of the Sasayama Group, southwest Japan, based on ostracode and conchostracan bio-stratigraphy and zircon fission-track dating

The age of the non-marine Cretaceous Sasayama Group, distributed in western Honshu, Japan, was reassessed based on ostracod and conchostracan bio-stratigraphy, and zircon fission-track dating. The ostracod genera Mongolocypris and Eucypris from the lower part of the Sasayama Group, combined with the conchostracan genera Yanjiestheria and Nemetheria from the upper part of the group, suggest an age range from Albian to Cenomanian. Zircon fission-track dating of the lower and upper parts of the group yields ages of 106±9, 100.9±8.4, and 96.1±7.4 Ma, also indicating a range from Albian to Cenomanian. These data indicate that deposition of the Sasayama Group began about 30 Ma later than previously thought.

Allozymic Variation in the Japanese Clawed Salamander,Onychodactylus japonicus(Amphibia: Caudata: Hynobiidae), with Special Reference to the Presence of Two Sympatric Genetic Types

We conducted an electrophoretic survey to examine geographic genetic variation in samples from 17 localities of the Japanese clawed salamander, Onychodactylus japonicus. This species was divided into six genetic groups (N-Tohoku, S-Tohoku, Tsukuba, SW-Honshu, Kinki, and Shikoku) that were largely concordant with clades or subclades recognized in our previous mtDNA study. Although the relationships among these six groups were not clarified, genetic distances between them were not small (mean Nel's D=0. 146-0.471). Among these groups, the geographically isolated Tsukuba group was genetically distinct, possibly as a result of population isolation. In a locality of western Honshu, two groups, SW-Honshu and Shikoku, were found to occur sympatrically. Although several presumable hybrid individuals were found, hybridization between these two groups seemed to occur very rarely. These results indicate that the Shikoku group is specifically distinct from the SW-Honshu group, whose range includes the type locality of O. japonicus.

Japanese species of the genus Oyamia (Plecoptera: Perlidae), with notes on O. nigribasis from Korea

A new species of Oyamia, O. cryptomeria, is described from western Honshu, Japan. The other two Japanese species, Oyamia lugubris (McLachlan) and O. seminigra (Klapálek), are redescribed. The new species is distinguished from the other species of Oyamia by the male genitalia and punctures on the egg. The O. seminigra complex is proposed for the new species and O. seminigra. The two species in the complex and the other Japanese species, O. lugubris, share some characteristics of larvae and male genitalia. An only single representative of the genus from the continent, O. nigribasis Banks, has different characteristics from the Japanese species. An additional characteristic of the genus is a feature of the mouthparts; i.e. a row of setae on the inner side of the larval lacinia.

The reproductive ecology of the southern red tabira bitterling Acheilognathus tabira jordani in Japan

The life history, population and reproductive variables of the southern red tabira bitterling Acheilognathus tabira jordani were investigated in a lowland reach of the River Ohara in Shimane Prefecture, western Honshu, Japan. Acheilognathus t. jordani, like all other species of bitterling, lays its eggs on the gills of freshwater mussels. It was the only species of bitterling present in the study reach, and three species of bivalve mussel were available to it for spawning: Anemina arcaeformis, Anodonta lauta and Corbicula leana. Spawning by A.t. jordani was recorded between early April and early July in 2003 and began at a size of 38. 0 mm standard length (L(S)) in the 1+ age class. Ovipositor length (L(OP)) during oviposition was positively correlated with female L(S), and showed significant seasonal variation, with a mean +/-s.d.L(OP) of 27. 5 +/- 5. 3 mm ranging from 16. 8 to 42. 0 mm during the spawning period, which was shorter than that of a previously studied A. t. tabira population. Eggs of this subspecies are relatively long and elliptic in shape, with a volume of c. 2. 4 mm(3). Egg number correlated positively with female L(S) and both egg shape and volume changed significantly with season. The population size of adults was estimated to be 850 individuals, and comprised age 0+ to 3+ individuals with L(S) ranging from 12. 0 to 72. 2 mm. The population sex ratio was significantly female biased, with seven females: three males. Egg shape and size and L(OP) during oviposition in the present A. tabira population may be the result of local adaptations to the mussel species utilized and no competition with other bitterling species for spawning sites.

Phylogeography of an ambrosia beetle, Xylosandrus crassiusculus (Motschulsky) (Coleoptera: Curculionidae: Scolytinae), in Japan

We examined the genetic structure of populations of an ambrosia beetle, Xylosandrus crassiusculus. Specimens were collected from 22 sites in Japan and their genetic structure was studied using a portion of the mitochondrial cytochrome oxidase I gene. Phylogenetic analysis revealed three distinct lineages (clades A, B and C), each of which was divided into two subclades (A1, A2, B1, B2, C1 and C2). Subclade A1 had 17 haplotypes from Hokkaido, Honshu and Kyushu populations, subclade A2 5 haplotypes mainly from Shikoku populations, subclade B1 15 haplotypes from central and western Honshu and Amami populations, subclade B2 2 haplotypes only from Naha population, subclade C1 4 haplotypes from Amami and Naha populations, and subclade C2 5 haplotypes only from Ishigaki population. Analysis of molecular variance detected genetic differentiation among populations. The data imply that the genetic structure of Japanese populations of X. crassiusculus has been affected by the geological history of the Japanese islands, but that the mtDNA phylogeographic pattern is so complex that we could not infer any simple scenario of population history in X. crassiusculus.

Occurrence of Epidermoptid Mites (Acari: Astigmata: Epidermoptidae) in Japan, with its Hyperparasitic Record on the Louse Fly Ornithomya avicularia aobatonis (Diptera: Hippoboscidae)

This report describes the hyperparasitism of Hemimyialges macdonaldi (Evans, Fain, and Bafort) (Acari: Astigmata: Epidermoptidae) on louse flies Ornithomya avicularia aobatonis (Matsumura) (Diptera: Hippoboscidae) found on a Eurasian Sparrowhawk Accipiter nisus nisosimilis (Tickell) (Falconiformes: Accipitridae) in western Honshu, Japan. This is the first record of the family Epidermoptidae in Japan. Moreover, this is the first case of hyperparasitism on louse flies in Japan and the first record of mite/fly and mite/bird host. Gravid female, nongravid female, immature male, and the egg of H. macdonaldi are figured.

A faunistic study on the dung beetles (Coleoptera: Scarabaeoidea) from Oki Islands off western Honshu, Japan

A faunistic study on the dung beetles (Coleoptera: Scarabaeoidea) from Oki Islands off western Honshu, Japan

Assessing bottom structure influence on fish abundance in a marine hill by using conjointly acoustic survey and geographic information system

Acoustic survey and a geographic information system (GIS) were used conjointly to estimate the significance of bottom substrate to explain fish abundance distribution in the complex topography context of a marine hill. The survey was conducted in the Hachirigase hill, off south- western Honshu Island in the Sea of Japan. Analysis of acoustic data focused on a 10-m thick layer beginning at the bottom, assuming that bottom influence does not exceed this distance. Area backscattering strength (Sa) values were rescaled in order to reflect real differences before being analyzed. Results show that the influence of the different parameters taken into account (bottom depth, bottom substrate and water temperature) varies widely from one place to another. Bottom substrate is above all important in the zone located to the west of the peak. The kriging and stratification methods were applied to the Sa distribution for estimating the total Sa in the hill. Differences between results are discussed. Conjoint use of acoustic survey and GIS is an effective method for analyzing and estimating fish abundance distribution in a marine hill.

Genetic characteristics of three recently discovered populations of the tideland snail Cerithidea djadjariensis (Martin) (Mollusca, Gastropoda) from the Pacific coast of the eastern Japan

The genetic characteristics of three populations of the tideland snail Cerithidea djadjariensis (Martin) that were recently discovered on the Pacific coast of the eastern Japan were compared with other Japanese conspecific popu- lations of this snail on the basis of the nucleotide sequences of mitochondrial DNA. Two populations from the Pacific coast of northeastern Honshu, the Japanese mainland, showed lower genetic diversity than and no significant differentia- tion from populations in western Honshu and Kyushu. The foundation of these populations might be attributed to range expansion along the coast, probably due to global warming. On the other hand, the population in Tokyo Bay, which was rediscovered in 2001 on an artificial tideland, was shown to be genetically different from all other Japanese populations whose genetic structures have been analyzed. It is suggested that this population was founded by human-mediated intro- duction such as transportation with short-necked clams, ballast water, or hull fouling.

Effects of Cutting Management on the Vegetational Changes of the Zoysia-Pteridium-type Pasture in Western Honshu

Effects of Cutting Management on the Vegetational Changes of the Zoysia-Pteridium-type Pasture in Western Honshu

Chronospatial variation of dental size of Holocene Japanese wild pigs (Sus scrofa leucomystax)

The lower teeth of the Japanese wild pigs (Sus scrofa leucomystax) from various geographical locations both archaeological and modern were investigated. Buccolingual measurements of the lower third and fourth premolars, and first and second molars are used to compare the regional and temporal differences in dental size of pigs in the Japanese Archipelago.Similar geographical variations in size of Jomon and modern wild pigs in Japan are observed in our study. The size of pigs from northern localities are larger compared to those from southern localities. Populations from Kyushu are distinctively small in dental size compared to the Honshu in both the Jomon and modern populations.A different pattern is observed in the Yayoi samples. The pigs from the Yayoi Period show a west-east cline in their size where the populations in the west being larger than those of east. Interestingly to note is that the size of pigs are significantly different between the sites in the northern Kyushu as well as in the western Honshu. The variation in a single region exceeds the geographical variations observed in the Jomon or in the modern samples. We can supose that most of these individuals were brought in from outside the Archipelago. It is a necessity to understand the variation of the modern and archaeological pigs in the Asian continent in order to further discuss the issue morphometrically.

Reassessing the concept of the ‘Neolithic’ in the Jomon of Western Japan

The concept of the Mesolithic/Neolithic transition is difficult to apply in the Japanese archipelago. The earliest pottery usage occurs in late Palaeolithic contexts. Holocene foragers lived in stable, permanent village settlements and constructed large scale monuments, and the first real ‘agriculture’ arrived as part of a cultural package which also included metallurgy. This paper will examine the use of the term ‘Neolithic’ in the history of Japanese archaeology, with particular emphasis on what happened in the western part of the archipelago in the latter part of the Jomon period (c. 5000 BC – c. 500 BC). Recent investigations in Kyushu and Western Honshu are leading to a re-assessment of the nature of Jomon culture and society in this region, traditionally considered to have ‘lagged behind’ the more developed societies of the eastern part of the archipelago, expressed in part through much lower population densities.

Low genetic diversities in isolated populations of the Asian black bear (Ursus thibetanus) in Japan, in comparison with large stable populations

Populations of the Asian black bear (Ursus thibetanus) are relatively large and continuous in central Honshu, the main island of Japan, but they are isolated in western Honshu. To clarify the degree of genetic isolation of the populations in western Honshu, we compared the genetic diversities of four populations in western Honshu with that of one of the continuous populations of central Honshu. Three of the four western Honshu populations were isolated and the other was continuous with the central Honshu populations on a geographical distribution basis. The genotypes at 10 microsatellite loci of the sampled individuals were determined and the genetic structures of the populations examined. Genetic diversities were significantly lower in the isolated populations than in the continuous populations. The continuous population in central Honshu had high levels of genetic diversity, comparable to those in populations of the American black bear (Ursus americanus) and the brown bear (Ursus arctos). The genetic distances between the two continuous populations were smallest, even though their geographic distance was largest (>200 km) among all the pairs of neighboring populations examined. Low genetic diversity within the isolated populations suggested genetic drift due to the small population size; the genetic differentiation among the populations indicated low rates of gene flow among them.