Temperate Region Of Japan Research Articles

寒冷地における水稲のタイヌビエに対する生育抑制力を簡易に評価する方法

寒冷地における水稲のタイヌビエに対する生育抑制力を簡易に評価する方法

寒冷地における競争力の強い水稲品種によるタイヌビエの生育抑制の過程

寒冷地における競争力の強い水稲品種によるタイヌビエの生育抑制の過程

寒冷地における地上部形態を異にする水稲品種間でのタイヌビエ必要除草期間の差異

寒冷地における地上部形態を異にする水稲品種間でのタイヌビエ必要除草期間の差異

Climatic responses of biomass production and grain yield in Japanese high-yielding rice cultivars under different transplanting times

Planting time is one of the management methods determining yield potential in rice. The aims of the present study were to determine whether early transplanting improves yield potential in temperate regions of Japan, and to identify quantitative influences of climatic factors on crop productivity. We evaluated differences in biomass production and yield formation under three transplanting times for high-yielding cultivars having different heading characteristics. Early transplanting extended growth duration, but did not increase biomass production before heading, resulting in no improvement in total spikelet number and yield potential. For all the cultivars, cumulative air temperature better explained differences in biomass production under different transplanting times than did cumulative solar radiation. The results indicate that early-transplanted plants could not effectively utilize solar radiation for CO2 assimilation and that early biomass production in early-transplanted plants was constrained by low temperature. On the other hand, biomass production after heading and grain filling in late-heading cultivars were reduced with late transplanting time, owing to lower solar radiation and lower temperature. These results suggest that avoiding late transplanting can increase final biomass as well as acquire stable and high grain yield in late-heading cultivars in temperate regions, even if early biomass production after transplanting is reduced by low temperature. Two indica-dominant cultivars showed the highest grain yield and biomass productivity in the present study, but showed higher base temperature for biomass production, indicating that inidica-dominant cultivars were susceptible to low temperature. Development of a management method and genetic modification to promote early biomass productivity at low temperatures is necessary for further improvement of yield potential of high-yielding cultivars in temperate regions.

Molecular Cytogenetic Analysis of the Scleractinian CoralAcropora solitaryensisVeron & Wallace 1984

We performed a molecular cytogenetic investigation of the scleractinian coral Acropora solitaryensis, which is dominant in the temperate region of Japan (30-35°N). Molecular cytogenetic analysis, using fluorescence in situ hybridization (FISH), was carried out for karyotyping and gene mapping. We propose the karyotype of this coral (2n = 30) based on C-banding and FISH analyses. FISH mapping of the rRNA gene was carried out with a probe generated by PCR amplification using rRNA gene primers. Furthermore, the telomeres and centromeres of all chromosomes were visualized using FISH. By comparative genomic hybridization using DNA from sperm and unfertilized eggs of this coral, we offer evidence suggesting the existence of sex chromosomes in this species. Collectively, these data advance our understanding of coral genetics.

Distribution and reproduction of the temperate-specific morphotype of the coral Favites flexuosa in the subtropical region, Lyudao, Taiwan

Favites flexuosa is one of the abundant coral species in the temperate regions of Japan. Although the species ranges widely, from tropical to temperate regions of the Indo-Pacific, colonies of this species living in temperate areas exhibit specific morphological features (in terms of color and skeletal attributes). In addition, the temperate-specific morphotype is limited in distribution to the temperate regions of Japan and has not been recorded in subtropical Okinawa. In the present study, we recorded the temperate morphotype in subtropical Lyudao (Green Island), Taiwan, suggesting that the morphotype is more widely distributed than previously thought and may have colonized temperate Japan directly from Lyudao. We describe the first records of spawning at Lyudao, Taiwan, and also at Wakayama in temperate Japan. In laboratories located in either region, spawning was observed between 30 min and 1 h after sunset. Intraspecific crossing of morphotype samples from either region revealed that the fertilization rates were high (>90%). In addition, we crossed F. flexuosa with Diploastrea favus at Lyudao. The two species hybridized successfully although the fertilization rate was relatively low.

日本の亜熱帯域と温帯域におけるキクメイシ <i>Dipsastraea speciosa </i>（Dana, 1846）の骨格成長

日本の亜熱帯域と温帯域におけるキクメイシ <i>Dipsastraea speciosa </i>（Dana, 1846）の骨格成長

Phylogenetic and taxonomic status of the coral Goniopora stokesi and related species (Scleractinia: Poritidae) in Japan based on molecular and morphological data

Background: Goniopora stokesi is an uncommon species mainly found in tropical and subtropical regions but was also reported in temperate regions of Japan. This species has two unique characteristics. First, it does not typically attach to hard substrates, i.e., it is free-living. Although non-free-living colonies were reported, it is unclear whether their morphologies exhibit intraspecific or interspecific differences. Second, they can asexually form daughter colonies, which are secondary colonies that grow on the surface (coenosac) of a parent colony and subsequently detach. To date, this specific characteristic has not been reported in Japan, and it is not clear whether this species occurs in Japan. Results: To clarify the taxonomic status of this species, we investigated its reproductive mechanism in Japan and morphologically and genetically analyzed specimens collected from both subtropical and temperate regions. We found that this species forms daughter colonies in Okinawa, Japan and that free-living colonies in the temperate region, which were formerly recognized as G. stokesi, likely constitute a morphological variation of a separate species. In addition, all non-free-living colonies with G. stokesi-like morphologies were also morphological variations of other species. Conclusions: Overall, free-living colonies with large, deep calices, thin walls, and well-developed epitheca on the underside were G. stokesi, whereas other free-living and all non-free-living G. stokesi-like colonies belonged to other species, such as Goniopora djiboutiensis.

Evidence of the existence of a toxic form of Cylindrospermopsis raciborskii (Nostocales, Cyanobacteria) in Japan

SUMMARYCylindrospermopsis raciborskii is a common, bloom‐forming, planktonic, freshwater cyanobacterium. Toxic populations producing cylindrospermopsin can cause water‐safety problems. Although C. raciborskii is distributed worldwide, the presence of cylindrospermopsin‐producing strains of C. raciborskii was initially reported only in Australia and recently in Thailand. Here, we report the isolation of a toxic strain of C. raciborskii (ISG9) from a freshwater sample collected in Okinawa in 2008. This is the first report describing toxin expression in this species in Japan, detected from a subtropical area. The C. raciborskii species is known to produce cylindrospermopsin as a dominant toxin; however, in this new isolate, the dominant toxin expressed was deoxy‐cylindrospermopsin. The discovery of a toxic strain of C. raciborskii in southern Japan emphasizes the need for basic monitoring schemes for this species in water supplies located in the temperate regions of Japan because of its possible expansion and distribution to other geographic areas.

Symbiodinium Clade C Dominates Zooxanthellate Corals (Scleractinia) in the Temperate Region of Japan

Endosymbiotic algae of the genus Symbiodinium have been divided into nine clades (A-I) following genetic classification; some clades are known to have physiological properties that enable the coral hosts to adapt to different environmental conditions. To understand the relationships of coral-alga symbioses, we focused on Symbiodinium diversity in zooxanthellate corals living under the severe environmental conditions of the temperate region (30°-35°N) of Japan. We investigated Symbiodinium clades in 346 colonies belonging to 58 coral species from six locations. We then selected three coral species-Acropora hyacinthus, Acropora japonica, and Cyphastrea chalcidicum-to investigate whether Symbiodinium clades changed during winter or summer over the course of year (May 2009-Apr 2010) in Tanabe Bay, Japan. Three Symbiodinium clades (C, D, and F) were detected in corals in the temperate region. Notably, 56 coral species contained Symbiodinium clade C. Oulastrea crispata predominantly contained clade D, but traces of clade C were also detected in all samples. The temperate-specific species Alveopora japonica contained clades C and F simultaneously. Seasonal change of symbiont clades did not occur in the three coral species during the investigation period where SSTs range on 12.5-29.2°C. However, we found Acropora (2 spp.) and Cyphastrea (1 sp.) contained different subcladal types of clade C. These results reveal that most coral species harbored Symbiodinium clade C stably throughout the year, suggesting that Symbiodinium clade C shows low-temperature tolerance, and that two hypothetical possibilities; genetic differences of subcladal types generating physiological differences or wide physiological flexibility in the clade C.

Ontogenetic changes in accumulation of rhizomes in monoclonal patch of Miscanthus sinensis Anderss. in warm temperate region of Japan

To determine the main benefits of clonal expansion of Miscanthus sinensis patches (monoclones), we observed the annual pattern of the areal expansion of a number of M. sinensis patches and examined how the quantity of rhizomes in such patches is related to changes in their basal area. To forage for nutriments, a patch must continuously widen its habitat. Patches annually expanded centrifugally by sympodial branching of short rhizomes, which originated in tillering that occurred more than once a year. However, the basal area of the patches approached a ceiling as the patches aged. Both the number and the weight of rhizomes in the patches continued to increase as long as the basal area expanded. The mean weight of rhizomes in patches also initially increased quickly, but then reached a ceiling as the clones expanded. Similarly, the amount of reserve substance per shoot in the patches increased asymptotically along with the clonal expansion, depending on the rhizome mass allotted to each shoot. These results suggest that, in the clonal growth of M. sinensis patches, the accumulation of reserve matter in the rhizomes is more important than foraging in new areas.

Geographical distribution of myxomycetes on coniferous deadwood in relation to air temperature in Japan

This study obtained information on the biogeographical distribution of lignicolous myxomycetes in temperate regions in Japan. It examined how climatic variables are related to patterns of occurrence in myxomycete communities. Sixty-four taxa were recorded on coniferous wood in 15 forest sites in summer. Common species that were abundant and widely distributed in Japan included Stemonitis axifera, Lycogala epidendrum, and Cribraria cancellata. In addition, Lindbladia cribrarioides was characteristic on dead Pinus densiflora wood in southwestern Japan. The species diversity index (H’) of the myxomycete communities was positively correlated with the annual mean temperature. The distribution of myxomycete communities was analyzed using nonmultidimensional scaling (NMDS). The ecological nature of the gradients expressed by the first two NMDS axes was that the first axis was found to correspond strongly to changes in the average minimum temperature and the latitude, and the second axis was related to a complex of factors, including altitude. The relative abundance of certain species in a myxomycete community on Japanese red pine changed in relation to the annual mean temperature, e.g., Lycogala epidendrum correlated negatively while Stemonitopsis hyperopta did so positively. We conclude that air temperatures can be used to predict the geographical distribution of lignicolous myxomycetes in this temperate region of Japan.

Geographical distribution of myxomycetes on coniferous deadwood in relation to air temperature in Japan

This study obtained information on the biogeographical distribution of lignicolous myxomycetes in temperate regions in Japan. It examined how climatic variables are related to patterns of occurrence in myxomycete communities. Sixty-four taxa were recorded on coniferous wood in 15 forest sites in summer. Common species that were abundant and widely distributed in Japan included Stemonitis axifera, Lycogala epidendrum, and Cribraria cancellata. In addition, Lindbladia cribrarioides was characteristic on dead Pinus densiflora wood in southwestern Japan. The species diversity index (H’) of the myxomycete communities was positively correlated with the annual mean temperature. The distribution of myxomycete communities was analyzed using nonmultidimensional scaling (NMDS). The ecological nature of the gradients expressed by the first two NMDS axes was that the first axis was found to correspond strongly to changes in the average minimum temperature and the latitude, and the second axis was related to a complex of factors, including altitude. The relative abundance of certain species in a myxomycete community on Japanese red pine changed in relation to the annual mean temperature, e.g., Lycogala epidendrum correlated negatively while Stemonitopsis hyperopta did so positively. We conclude that air temperatures can be used to predict the geographical distribution of lignicolous myxomycetes in this temperate region of Japan.

White spot syndrome of Turbinaria peltata in the temperate region of Japan

White spot syndrome of Turbinaria peltata in the temperate region of Japan

Pathogen attack and spatial patterns of juvenile mortality and growth in a temperate tree, Prunus grayana

To examine whether the Janzen–Connell hypothesis is valid in temperate forests, we investigated the density, growth, mortality, and agents of mortality of seedlings and the density, size, and age of saplings of Prunus grayana Maxim. at three distances (0–3, 6–10, and 16–26 m) from conspecific adults in a temperate forest in Japan. An inoculation experiment was also conducted to test the host range of a leaf pathogen. The probability of mortality was highest at 0–3 m during the first 2 years of growth. Mortality mainly resulted from distance-dependent attack by two types of pathogen that caused damping-off epidemics and spot symptoms on leaves. The leaf pathogen was identified as Phaeoisariopsis pruni-grayanae Sawada, which infected many more seedlings of Prunus grayana than of the two other tree species tested in an inoculation experiment. The vertical and diameter growth was lowest at 0–3 m and highest at 16–26 m in both seedlings and saplings. As a result, the greatest number of large and older saplings was observed at 16–26 m. Our results demonstrate that the Janzen–Connell mechanism operates in a beech-dominated forest in the temperate region of Japan.

A STUDY OF MODULUS FOR EACH ASPHALT PAVEMENT LAYER IN THE NATIONAL ROADS IN HOKKAIDO

The first process of introducing a theoretical method into the design of asphalt pavement is to set the modulus and Poisson's ratio for each pavement layer. The numerical value gained by it significantly affects the subsequent multilayer elastic analysis. Unlike the temperate regions in Japan, however, cold and snowy Hokkaido has a history of setting unique regional standards of binder penetration, granular grading as well as other properties. In addition, the modulus for each pavement layer in the cold areas in Japan and those in the warm areas tend to be different. In this study, in order to establish a multilayer elastic theory for cold and snowy regions, the modulus for each pavement layer will be examined. This is based on FWD measurement results obtained from pavement testing on the major national roads in Hokkaido. The relationship between the temperature and the modulus of elasticity in an asphalt mixture layer and the range of modulus in granular will be explained.

Molecular phylogeography of two sibling species of Eurema butterflies

The common yellow butterfly Eurema hecabe is widely distributed in East Asia, and is one of the most burdensome species for taxonomists due to the numerous geographic and seasonal wing colour patterns. Moreover, within this species, individuals with a yellow wing fringe that occur in temperate regions of Japan (Y type) proved to be biologically different from others that occur widely in subtropical regions of Japan and all over East Asia (B type). To unveil the genetic variation within and between the two types, a total of 50 butterflies collected at 18 geographic localities in East Asia were examined for nucleotide sequence variation of three mitochondrial regions: cytochrome c oxidase subunit I (COI), cytochrome c oxidase subunit III (COIII) and NADH dehydrogenase subunit 5 (ND5). In addition, they were also examined for infection status with the endosymbiotic bacteria Wolbachia. The three mitochondrial sequences consistently showed that (i) Y type and B type were highly divergent, (ii) nucleotide variation within B type was very small although sampled from a geographically wide range, and (iii) a weak association existed between mitochondrial DNA haplotypes and Wolbachia infection status.

Comparison of stream benthic invertebrate assemblages among forest types in the temperate region of Japan

We compared benthic invertebrate assemblages among headwater streams in several forest types in Japan. Forests were divided into three clusters based on vegetation composition: old-growth broad-leaved forest, planted coniferous forest, and mixed forest. The numbers of individuals and families and the diversity (Shannon-Wiener) of benthic invertebrate assemblages did not differ significantly among the three forest clusters. However, principal components analysis of family abundance showed differences in the benthic invertebrate assemblages among the three forest clusters. No environmental factors were correlated with these differences. Benthic invertebrate assemblages differed depending on forest composition. The abundances of Taeniopterygidae and Athericidae in old-growth broad-leaved forest were significantly greater than in planted coniferous forest. The abundances of Heptageniidae, Baetiidae, Stenopsychidae, Uenoidae, Chironomidae, and Potamidae in planted coniferous forest were significantly greater than in old-growth broad-leaved forest. If the remaining old-growth broad-leaved forest were to be converted to coniferous plantation, species that inhabit old-growth forest may become extinct.

Effects of resource heterogeneity on nitrogen translocation within clonal fragments of Sasa palmata: an isotopic (15N) assessment.

Clonal fragments of the rhizomatous dwarf bamboo Sasa palmata, which widely predominates in temperate regions of Japan, were grown under heterogeneous resource conditions such as gap understories or nutrient-patchy grassland. Clonal fragments develop multiple ramets with long rhizomes and appear to be physiologically integrated by the translocation of assimilates. The glasshouse experiment reported here was designed to clarify the mechanisms of physiological integration of nitrogen more precisely. To assess how resource conditions influence the amount of nitrogen translocation, and which organ acts as the strongest sink, two experiments were conducted that traced movement of 15N label between interconnected pairs of ramets to compare homogeneous and heterogeneous light and soil nitrogen conditions. The amount of 15N translocated to leaves was between 9% and 11% greater in high-N and high-light ramets in the heterogeneous compared with homogeneous treatments. Under heterogeneous soil nitrogen conditions, translocation increased from individual ramets in resource-rich patches to ramets in resource-poor patches, while the reverse was true under heterogeneous light environments, reflecting differences in the positions of leaves that act as the strongest sinks. Neither the mass increments nor the total mass of clonal fragments was significantly affected by heterogeneity of either light or nutrients, possibly because the experimental period was too short for differences to manifest themselves. This study clearly demonstrated that nitrogen is readily translocated between ramets, particularly under heterogeneous resource conditions. The translocation patterns were governed by functional 'division of labour' mechanisms that resulted in net nitrogen movement from understory sites to gaps, thereby enhancing the carbon acquisition of the whole fragment. Thus, physiological integration may provide benefits for S. palmata when it is growing under heterogeneous conditions in which there are deficits of certain environmental resources.

Temperature-dependent development of the citrus psyllid, Diaphorina citri (Homoptera: Psylloidea), and the predicted limit of its spread based on overwintering in the nymphal stage in temperate regions of Japan

The citrus psyllid Diaphorina citri Kuwayama transferred huanglongbing (HLB) are distributed in the southern Islands (Yaku, 30°20� N, 130°30� E) of Japan. To predict the northern limit of the spread of the insect, I examined temperature-dependent development and determined the developmental zero of the insects in a laboratory. Eggs and nymphs were reared at temperatures of 15.0 to 32.5°C at an interval of 2.5°C with 16L : 8D on shoots of orange jasmine, Murraya exotica L. Nymphs at 15.0°C fail to develop to adults, and the mortality of those at 32.5°C increased. The incubation period decreased at higher temperatures, varying 15.0 to 2.5 d. These nymphs became adults in 36.3 d at 15.0°C and in 10.7 d at 30°C, but 16.8 d at 32.5°C. The developmental zero and effective accumulative temperatures were 13.66°C and 46.93 d-degrees in the egg group, 11.56°C and 192.27 d-degrees in the nymph group, respectively. Based on these results and winter temperatures, the northern limit of nymphal overwintering of the psyllid in Japan was predicted: the northern limit may be off the southern shores of Kyushu Island, southern Japan, and ca. 31°N.