研究者詳細 - 兵藤　不二夫

論文 - 兵藤　不二夫

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Linear relationship between carbon and nitrogen isotope ratios along simple food chains in marine environments

Maki Noguchi Aita, Kazuaki Tadokoro, Nanako O. Ogawa, Fujio Hyodo, Reiichiro Ishii, S. Lan Smith, Toshiro Saino, Michio J. Kishi, Sei-Ichi Saitoh, Eitaro Wada

JOURNAL OF PLANKTON RESEARCH 33 ( 11 ) 1629 - 1642 2011年11月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：OXFORD UNIV PRESS

To examine the relationship between carbon and nitrogen stable isotope (SI) ratios (delta C-13 and delta N-15) of zooplankton, we analyzed samples collected bimonthly from March to October 2009, from the euphotic layers of the Oyashio current along the A-line in the western North Pacific. Isotopic ratios of higher trophic levels such as predatory zooplankton and/or long-lived zooplankton varied little with season, while those of short-lived zooplankton were variable on the delta N-15-delta C-13 map. We also analyzed preserved samples taken from the warm-core ring 86-B derived from the Kuroshio extension region. Although the zooplankton groups in the two regions exhibited different values in delta N-15, the delta N-15 versus delta C-13 slopes for each ecosystem do not show significant differences. Statistical analysis conducted together with previously published data from the Antarctic Ocean and the Gulf of Alaska suggested a similar delta N-15 versus delta C-13 slope throughout the four regions. We attributed this common slope to physiological aspects of feeding processes (e. g. the kinetic isotope effects inherent in the processes of amino acid synthesis). The common pattern for all four oceanic regions suggests that SIs may be used to elucidate general patterns in ecosystems and biogeochemical cycles.

DOI： 10.1093/plankt/fbr070

笠岡湾干拓地における水質汚濁の現状と安定同位体比を用いた汚濁機構解析査読

前田守弘, 浅野裕一, 兵藤不二夫, 中島泰弘, 藤原拓, 永禮英明, 赤尾聡史

土木学会論文集G（環境） 67 ( 7 ) III_213 - III_222 2011年11月

Feeding habits of Hymenoptera and Isoptera in a tropical rain forest as revealed by nitrogen and carbon isotope ratios

F. Hyodo, Y. Takematsu, T. Matsumoto, Y. Inui, T. Itioka

INSECTES SOCIAUX 58 ( 3 ) 417 - 426 2011年8月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：SPRINGER BASEL AG

Despite the recognition of the functional role of Hymenoptera (ants, bees and wasps) and Isoptera (termites) in tropical ecosystems, their detailed feeding habits are not well known. To examine the feeding habits of these groups, we measured nitrogen (N) and carbon (C) stable isotope ratios (delta(15)N and delta(13)C) of hymenopterans (12 families, a parts per thousand yen16 genera and a parts per thousand yen32 species) and isopterans (one family and 10 species) collected in a tropical rain forest, Sarawak, Malaysia. We compared the isotopic signatures of these insects to those previously reported for other consumers collected in the same forest. The delta(15)N and delta(13)C values of these insects overlapped with those of the other consumers, indicating that they have access to diverse C and N sources in the forest. The delta(15)N values of ants and termites indicated that their feeding habits range along a continuum from herbivory (i.e. dependent on honeydew and nectar) to predation and from wood-feeders to soil-feeders, respectively. In addition, the delta(15)N values of wasps varied greatly from -0.1aEuro degrees (Braconidae sp.) to 8.6aEuro degrees (Bembix sp.), suggesting that their feeding habits also range from omnivory to predation. The ant species Camponotus gigas had delta(13)C values similar to those of invertebrate detritivores and omnivores rather than to those of invertebrate herbivores, although the diet of this species consists mostly of honeydew. This discrepancy suggests that the ant uses carbohydrates as an energy source, the isotopic signatures of which are not well retained in the body tissues. Values of both delta(15)N and delta(13)C of the predatory army ant Leptogenys diminuta and the soil-feeding termite Dicuspiditermes nemorosus did not differ significantly, indicating that both trophic level and the humification of feeding substrates can increase the isotopic signatures of terrestrial consumers.

DOI： 10.1007/s00040-011-0159-9

伏見城跡遺跡から出土した江戸時代人骨の安定同位体による食性分析

日下宗一郎, 五十嵐健行, 兵藤不二夫, 藤澤珠織, 片山一道

Anthropological science. Japanese series : journal of the Anthropological Society of Nippon : 人類學雜誌 119 ( 1 ) 9 - 17 2011年6月

記述言語：日本語出版者・発行元：日本人類学会

江戸時代は、急激な人口増加とその後の人口安定、また陸・海路による交易網の発達によって特徴づけられ、コメや野菜や魚介類を主要な食物としていたと言われる。そのような江戸時代の人々の食性を、遺跡から出土した人骨を用いて実証しようとするのが本研究である。伏見城跡遺跡(京都市)より出土した江戸時代人骨および動物骨からコラーゲンを抽出して、炭素および窒素の安定同位体比を測定した。合計で27個体(男性9個体、女性12個体、子ども6個体)の人骨を分析に用いた。それにより、伏見江戸時代人の食性、その性差を検討することを目的とした。江戸時代の伏見の人々は、タンパク質源を淡水魚類に強く依存した食生活、もしくは陸上生態系から得られるC3植物と海産あるいは淡水魚類などを主たるタンパク質源とする食生活を送っていた可能性を示した。江戸時代の都市では、食生活が米、野菜、魚介類からなり、アワやヒエ、キビなどC4植物の消費が少ないとする古記録を考慮に入れると、後者の食生活像が支持される。また、男性の炭素同位体比は女性よりも高く、より多くの海産魚類や貝類などを摂取していた可能性がある。また、年齢が上がると子どもの窒素同位体比は下がる傾向があり、これは母乳の摂取と離乳の開始に関連していると考えられる。(著者抄録)

DOI： 10.1537/asj.119.9

Long-term aboveground and belowground consequences of red wood ant exclusion in boreal forest

David A. Wardle, Fujio Hyodo, Richard D. Bardgett, Gregor W. Yeates, Marie-Charlotte Nilsson

ECOLOGY 92 ( 3 ) 645 - 656 2011年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ECOLOGICAL SOC AMER

Despite their ubiquity, the role of ants in driving ecosystem processes both aboveground and belowground has been seldom explored, except within the nest. During 1995 we established 16 ant exclusion plots of approximately 1.1 x 1.1 m, together with paired control plots, in the understory layer of a boreal forest ecosystem in northern Sweden that supports high densities of the mound-forming ant Formica aquilonia, a red wood ant species of the Formica rufa group. Aboveground and belowground measurements were then made on destructively sampled subplots in 2001 and 2008, i.e., 6 and 13 years after set-up. While ant exclusion had no effect on total understory plant biomass, it did greatly increase the relative contribution of herbaceous species, most likely through preventing ants from removing their seeds. This in turn led to higher quality resources entering the belowground subsystem, which in turn stimulated soil microbial biomass and activity and the rates of loss of mass and carbon (C) and nitrogen (N) from litter in litterbags placed in the plots. This was accompanied by losses of similar to 15% of N and C stored in the humus on a per area basis. Ant exclusion also had some effects on foliar stable isotope ratios for both C and N, most probably as a consequence of greater soil fertility. Further, exclusion of ants had multitrophic effects on a microbe-nematode soil food web with three consumer trophic levels and after six years promoted the bacterial-based relative to the fungal-based energy channel in this food web. Our results point to a major role of red wood ants in determining forest floor vegetation and thereby exerting wide-ranging effects on belowground properties and processes. Given that the boreal forest occupies 11% of the Earth's terrestrial surface and stores more C than any other forest biome, our results suggest that this role of ants could potentially be of widespread significance for biogeochemical nutrient cycling, soil nutrient capital, and sequestration of belowground carbon.

DOI： 10.1890/10-1223.1

Carbon and nitrogen stable isotope analysis on the diet of Jomon populations from two coastal regions of Japan

Soichiro Kusaka, Fujio Hyodo, Takakazu Yumoto, Masato Nakatsukasa

JOURNAL OF ARCHAEOLOGICAL SCIENCE 37 ( 8 ) 1968 - 1977 2010年8月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD

We report on a stable isotope paleodietary reconstruction of Jomon populations in Japan during the Middle to Final Jomon period (ca. 5000-2300 years BP), focusing on dietary differences within and among populations and between regions. Carbon and nitrogen isotope analysis was performed on human and faunal bone collagen from six coastal sites along the Inland Sea in the Sanyo (Ota, Funamoto, and Tsukumo) region and along Mikawa Bay and the Pacific Ocean in the Tokai (Kawaji, Yoshigo, and lnariyama) region. We found that carbon and nitrogen isotope ratios were positively correlated, indicating that the Jomon people consumed a mixed diet of marine (shellfish and marine fish) and terrestrial (C(3) plants and terrestrial mammals) protein. In the Ota samples (n = 25, during the Middle Jomon period, 5000-4000 years BP), sex was one of the main reasons for the intra-population dietary variation. Ota males consumed greater amounts of marine food, while Ota females consumed greater amounts of terrestrial food; these dissimilar diets may have been related to the sexual division of labor. Significant inter-population dietary differences were found, which may have been related to differences in age or site location. Notably, the two coastal regions showed clear isotopic differences. Nitrogen isotope ratios of individuals from the Sanyo region were significantly higher than ratios of individuals from the Tokai region. The individuals in the Sanyo region might have consumed a diet high in aquatic foods, particularly high trophic level marine fish, whereas the individuals in the Tokai region might have consumed a lot of marine shellfish. Another possible reason for the regional isotopic difference might have been different baseline of nitrogen isotope ratios of the marine ecosystems. (C) 2010 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.jas.2010.03.002

Linking aboveground and belowground food webs through carbon and nitrogen stable isotope analyses

Fujio Hyodo, Ayato Kohzu, Ichiro Tayasu

ECOLOGICAL RESEARCH 25 ( 4 ) 745 - 756 2010年7月

記述言語：英語出版者・発行元：SPRINGER TOKYO

Carbon and nitrogen stable isotope ratios (delta(13)C and delta(15)N) have been used for more than two decades in analyses of food web structure. The utility of isotope ratio measurements is based on the observation that consumer delta(13)C values are similar (< 1aEuro degrees difference) to those of their diet, while consumer delta(15)N values are about 3aEuro degrees higher than those of their diet. The technique has been applied most often to aquatic and aboveground terrestrial food webs. However, few isotope studies have examined terrestrial food web structure that includes both above- and belowground (detrital) components. Here, we review factors that may influence isotopic signatures of terrestrial consumers in above- and belowground systems. In particular, we emphasize variations in delta(13)C and delta(15)N in belowground systems, e.g., enrichment of (13)C and (15)N in soil organic matter (likely related to soil microbial metabolism). These enrichments should be associated with the high (13)C (similar to 3aEuro degrees) enrichment in belowground consumers relative to litter and soil organic matter and with the large variation in delta(15)N (similar to 6aEuro degrees) of the consumers. Because such enrichment and variation are much greater than the trophic enrichment generally used to estimate consumer trophic positions, and because many general predators are considered dependent on energy and material flows from belowground, the isotopic variation in belowground systems should be taken into account in delta(13)C and delta(15)N analyses of terrestrial food webs. Meanwhile, by measuring the delta(13)C of key predators, the linkage between above- and belowground systems could be estimated based on observed differences in delta(13)C of primary producers, detritivores and predators. Furthermore, radiocarbon ((14)C) measurements will allow the direct estimation of the dependence of predators on the belowground systems.

DOI： 10.1007/s11284-010-0719-x

The structure of a food web in a tropical rain forest in Malaysia based on carbon and nitrogen stable isotope ratios

Fujio Hyodo, Takashi Matsumoto, Yoko Takematsu, Tamaki Kamoi, Daisuke Fukuda, Michiko Nakagawa, Takao Itioka

JOURNAL OF TROPICAL ECOLOGY 26 205 - 214 2010年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：CAMBRIDGE UNIV PRESS

Carbon and nitrogen stable isotope ratios (delta(13)C and delta(15)N) have been used to study the structure of food webs. However, few studies have examined how a terrestrial food web can be depicted by this technique. We measured delta(13)C and delta(15)N in various consumers of four trophic groups (detritivores, herbivores. omnivores and predators), including vertebrates and invertebrates (14 orders, >= 24 families). as well as canopy and understorey leaves in a tropical rain forest in Malaysia. We found that. delta(13)C and delta(15)N of the consumers differed significantly among the trophic groups. The predators had significantly, higher delta(13)C than the herbivores, and were similar in delta(13)C to the detritivores, suggesting that most. predators examined depend largely, on below-ground food webs. delta(15)N was higher in predators than detritivores by about, 3 parts per thousand. The comparison of delta(13)C in plant materials and herbivores suggests that most. herbivores are dependent on C fixed in the canopy, layers. The vertebrates had significantly higher delta(15)N and delta(13)C than the invertebrates of the same trophic group. likely reflecting differences in the physiological processes and/or feeding habits. This study indicates that stable isotope techniques can help better Understanding of the terrestrial food webs in terms of both trophic level and the linkage of above and below-ground systems.

DOI： 10.1017/S0266467409990502

A strontium isotope analysis on the relationship between ritual tooth ablation and migration among the Jomon people in Japan

Soichiro Kusaka, Atsushi Ando, Takanori Nakano, Takakazu Yumoto, Eriko Ishimaru, Minoru Yoneda, Fujio Hyodo, Kazumichi Katayama

JOURNAL OF ARCHAEOLOGICAL SCIENCE 36 ( 10 ) 2289 - 2297 2009年10月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD

Distinct patterns can be discerned in the extensive ritual tooth ablation found among the human skeletal remains of the Late-Final Jomon period (ca. 3200-2800 cal BP) in Japan. Based on comparative observations of sex and grave patterns in the skeletal remains, two major patterns in ritual tooth ablation, termed type 41 and type 2C, have been assigned to locals and immigrants, respectively. In order to test this hypothesis, strontium (Sr) isotope ((87)Sr/(86)Sr) analyses were performed on human skeletal remains from the Yoshigo shell mound in Aichi Prefecture, central Japan. Plants in the surrounding area were also examined to illustrate the geographic (87)Sr/(86)Sr distribution. The Sr isotopic variation in human tooth enamel ((87)Sr/(86)Sr = 0.70868-0.71028) was greater than that in human bones ((87)Sr/(86)Sr = 0.70871-0.70943). Individuals with higher Sr isotope ratios in their tooth enamel than seawater Sr values of 0.7092 can be identified as immigrants (36% of population). The presence of these isotopically identified immigrants between both type 2C and type 41 individuals does not support the previous hypothesis. The intra-population (87)Sr/(86)Sr distribution of tooth enamel of type 2C individuals showed a significantly higher mean ratio than that of type 41 individuals, suggesting a higher proportion of immigrants among the former. (C) 2009 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.jas.2009.06.013

Effect of ecosystem retrogression on stable nitrogen and carbon isotopes of plants, soils and consumer organisms in boreal forest islands

Fujio Hyodo, David A. Wardle

RAPID COMMUNICATIONS IN MASS SPECTROMETRY 23 ( 13 ) 1892 - 1898 2009年7月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：JOHN WILEY & SONS LTD

In the prolonged absence of catastrophic disturbance, ecosystem retrogression occurs, and this involves increased nutrient limitation, and reduced aboveground and belowground ecosystem processes rates. Little is known about how the nitrogen and carbon stable isotope ratios (delta(15)N and delta(13)C) of plants, soils and consumer organisms respond to retrogression in boreal forests. We investigated a 5000 year chronosequence of forested islands in the boreal zone of northern Sweden, for which the time since lightning-induced wildfire increases with decreasing island size, leading to ecosystem retrogression. For this system, tissue delta(15)N of three abundant plant species (Betula pubescens, Vaccinium myrtillus and Pleurozium schreberi) and humus all increased as retrogression proceeded. This is probably due to enhanced ecosystem inputs of N by biological fixation, and greater dependency of the plants on organic N during retrogression. The delta(13)C of B. pubescens and plant-derived humus also increased during retrogression, probably through nutrient limitation increasing plant physiological stress. Unlike the plants, delta(15)N of invertebrates (lycosid spiders and ants) did not increase during retrogression, probably because of their partial dependence on aquatic-derived prey that had a variable delta(15)N signature. The delta(13)C of the invertebrates increased as retrogression proceeded and converged towards that of an aquatic prey source (chironomid flies), suggesting increased dependence on aquatic-derived prey during retrogression. These results show that measurement of delta(15)N and delta(13)C of plants, soils, and consumers across the same environmental gradient can provide insights into environmental factors that drive both the aboveground and belowground subsystems, as well as the linkages between them. Copyright (C) 2009 John Wiley & Sons, Ltd.

DOI： 10.1002/rcm.4095

Flower orientation enhances pollen transfer in bilaterally symmetrical flowers

Atushi Ushimaru, Ikumi Dohzono, Yasuoki Takami, Fujio Hyodo

OECOLOGIA 160 ( 4 ) 667 - 674 2009年7月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：SPRINGER

Zygomorphic flowers are usually more complex than actinomorphic flowers and are more likely to be visited by specialized pollinators. Complex zygomorphic flowers tend to be oriented horizontally. It is hypothesized that a horizontal flower orientation ensures effective pollen transfer by facilitating pollinator recognition (the recognition-facilitation hypothesis) and/or pollinator landing (the landing-control hypothesis). To examine these two hypotheses, we altered the angle of Commelina communis flowers and examined the efficiency of pollen transfer, as well as the behavior of their visitors. We exposed unmanipulated (horizontal-), upward-, and downward-facing flowers to syrphid flies (mostly Episyrphus balteatus), which are natural visitors to C. communis. The frequency of pollinator approaches and landings, as well as the amount of pollen deposited by E. balteatus, decreased for the downward-facing flowers, supporting both hypotheses. The upward-facing flowers received the same numbers of approaches and landings as the unmanipulated flowers, but experienced more illegitimate landings. In addition, the visitors failed to touch the stigmas or anthers on the upward-facing flowers, leading to reduced pollen export and receipt, and supporting the landing-control hypothesis. Collectively, our data suggested that the horizontal orientation of zygomorphic flowers enhances pollen transfer by both facilitating pollinator recognition and controlling pollinator landing position. These findings suggest that zygomorphic flowers which deviate from a horizontal orientation may have lower fitness because of decreased pollen transfer.

DOI： 10.1007/s00442-009-1334-9

Nitrogen-stable isotopic signatures of basal food items, primary consumers and omnivores in rivers with different levels of human impact

Ayato Kohzu, Ichiro Tayasu, Chikage Yoshimizu, Atsushi Maruyama, Yukihiro Kohmatsu, Fujio Hyodo, Yukio Onoda, Akitake Igeta, Kiyoshi Matsui, Takanori Nakano, Eitaro Wada, Toshi Nagata, Yasuhiro Takemon

ECOLOGICAL RESEARCH 24 ( 1 ) 127 - 136 2009年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：SPRINGER TOKYO

We examined how nitrogen-stable isotopic signatures of food web components (basal resources, primary and lower consumers, and omnivores) in rivers change with increasing levels of human population density (HPD) in their watersheds. Samples were collected from 22 rivers flowing in the Lake Biwa basin, Japan. Among three potential resources at the base of food webs (epilithon, benthic and suspended particulate organic matter), the mean isotopic values (delta(15)N) of the epilithon (4.5-7.8%) were consistently higher than those of other items (1.9-4.2%) and displayed the most pronounced elevation (by 3.3%) with increasing HPD. The mean delta(15)N values of the individual taxa of lower consumers (bivalve, snail and caddisfly) tended to increase with increasing HPD, although the pattern and the extent of the elevation were highly variable among the taxa. These results suggest a taxon-specific feature in the N source (or sources) of lower consumers. Our data suggested that human activities (e.g. nutrient loading) potentially induce changes in the N baselines of river food webs. The major N source of bivalves appeared to be shifted from suspended particulate organic matter to other items with increasing HPD. Trophic levels of goby fish (Rhinogobius sp. OR) and shrimp (Palaemon paucidens), being estimated to be at 2.4-3.8 and 2.1-3.4, respectively, did not differ significantly among rivers with different HPD levels.

DOI： 10.1007/s11284-008-0489-x

Within-nest abundance of a tropical cockroach Pseudoanaplectinia yumotoi associated with Crematogaster ants inhabiting epiphytic fern domatia in a Bornean dipterocarp forest

Yoko Inui, Hiroshi O. Tanaka, Fujio Hyodo, Takao Itioka

JOURNAL OF NATURAL HISTORY 43 ( 19-20 ) 1139 - 1145 2009年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：TAYLOR & FRANCIS LTD

Many epiphytic ferns in tropical forest canopies have domatia that provide habitat for arboreal arthropods such as ants. Two species of fern that were predominantly occupied by Crematogaster difformis ants were collected from the canopy of a forest in Borneo. In the fern domatia, two cockroach species, Pseudoanaplectinia yumotoi and Blatta sp., were found to live with C. difformis. Pseudoanaplectinia yumotoi were found in large numbers and accounted for approximately 20% of the total arthropod population, while Blatta sp. comprised only 1% of the arthropods living in the domatia. Behavioural experiments were conducted to evaluate the response of C. difformis workers to newly introduced cockroaches of each species and to allospecific ant workers. Crematogaster difformis workers were highly aggressive and quickly attacked allospecific workers. Both cockroach species could fend off ant attacks; however, dead Blatta sp. were often attacked by the ants while dead P. yumotoi were infrequently bothered.

DOI： 10.1080/00222930902807734

Use of Stable Nitrogen Isotope Signatures of Riparian Macrophytes As an Indicator of Anthropogenic N Inputs to River Ecosystems

Ayato Kohzu, Toshihiro Miyajima, Ichiro Tayasu, Chikage Yoshimizu, Fujio Hyodo, Kiyoshi Matsui, Takanori Nakano, Eitaro Wada, Noboru Fujita, Toshi Nagata

ENVIRONMENTAL SCIENCE & TECHNOLOGY 42 ( 21 ) 7837 - 7841 2008年11月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER CHEMICAL SOC

Deterioration of aquatic ecosystems resulting from enhanced anthropogenic N loading has become an issue of increasing concern worldwide, and methods are needed to trace sources of N in rivers. Because nitrate from sewage is enriched in N-15 relative to nitrate from natural Soils, delta N-15 values of stream nitrate (delta N-15(nitrate)) should be an appropriate index of anthropogenic N loading to rivers, as should the delta N-15 values of riparian plants (delta N-15(plant)) because they are consumers of nitrate. We determined the delta N-15 values of stream nitrate and six species of riparian macrophytes in 31 rivers in the Lake Biwa Basin in Japan. We then tested the correlation between these values and various land-use parameters, including the percentage of land used for residential and agricultural purposes as well as for natural areas. These delta N-15 values were significantly positively correlated with land use N that had a high N load (i.e., residential or agricultural use) and significantly negatively correlated with forest N. These findings indicate that (delta N-15 values of stream nitrate and riparian plants might be good indicators of anthropogenic inputs of nitrogen.

DOI： 10.1021/es801113k

Changes in stable isotopes, lignin-derived phenols, and fossil pigments in sediments of Lake Biwa, Japan: Implications for anthropogenic effects over the last 100 years

Fujio Hyodo, Narumi Tsugeki, Jun ichi Azuma, Jotaro Urabe, Masami Nakanishi, Eitaro Wada

Science of the Total Environment 403 ( 1-3 ) 139 - 147 2008年9月

Variability in stable isotope ratios in two Late-Final Jomon communities in the Tokai coastal region and its relationship with sex and ritual tooth ablation

Soichiro Kusaka, Soichiro Kusaka, Takeyuki Ikarashi, Fujio Hyodo, Takakazu Yumoto, Kazumichi Katayama

Anthropological Science 116 ( 2 ) 171 - 181 2008年9月

Gradual enrichment of ¹⁵N with humification of diets in a below-ground food web: Relationship between ¹⁵N and diet age determined using ¹⁴C

F. Hyodo, I. Tayasu, S. Konaté, J. E. Tondoh, P. Lavelle, E. Wada

Functional Ecology 22 ( 3 ) 516 - 522 2008年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：WILEY-BLACKWELL

1. Stable nitrogen (N) isotope has been widely used to disentangle food webs and to infer trophic positions of organisms based on an assumption that the stepwise enrichment occurs along trophic levels. The enrichment of N in soil organisms with diet humification has also been reported, but the underlying mechanism has not been fully examined. 2. To examine the effect of diet humification on N, we estimated the stable N isotope ratios and diet ages of earthworms and termites. These organisms feed on organic matter with various degrees of humification, ranging from undecomposed plant materials to humified organic matter (soil organic matter), in a gallery forest and a savanna in the Ivory Coast. We defined diet age as the time elapsed since carbon (C) in the diet of earthworms and termites was fixed from atmospheric CO by photosynthesis; it was estimated by comparing the radiocarbon ( C) content of these organisms to atmospheric CO records. 3. Stable N isotope ratios increased along the humification gradient of diets, and values for earthworms and termites varied from 1.8‰ to 9.9‰ and from -1.5‰ to 15.9‰, respectively. Epigeic (litter-feeding) earthworms had younger diet ages (2-4 years), whereas endogeic (soil-feeding) earthworms generally exhibited older diet ages (5-9 years). Grass-feeding termites had young diet ages (2 years), and wood/soil-feeding termites had the oldest diet ages (c. 50 years). Soil-feeding termites were similar in diet age (7-12 years) to wood feeders (8-11 years), with the exception of one species (18-21 years) that consumes large-diameter wood. 4. A significant positive relationship was found between diet ages and stable N isotope ratios of the two groups in the savanna. This relationship held in the gallery forest when termites feeding on woody tissues were not considered. These results show that the stable N isotope ratios of organisms can increase with diet age, unless C in the diet has been stored as organic matter, such as woody tissue, that is able to age without being subject to humification processes. 5. Given that above-ground food webs are often sustained directly by material and energy flow from below-ground food webs, in addition to trophic interactions, gradual enrichment of N with the humification of below-ground diets should be considered when interpreting stable N isotope ratios of terrestrial food webs. © 2008 The Authors. 15 15 14 14 15 2 2

DOI： 10.1111/j.1365-2435.2008.01386.x

Effect of agriculture on water quality of Lake Biwa tributaries, Japan

Takanori Nakano, Ichiro Tayasu, Yoshihiro Yamada, Takahiro Hosono, Akitake Igeta, Fujio Hyodo, Atsushi Ando, Yu Saitoh, Takuya Tanaka, Eitaro Wada, Shigeo Yachi

SCIENCE OF THE TOTAL ENVIRONMENT 389 ( 1 ) 132 - 148 2008年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE BV

We investigated the effects of natural environments and human activity on Lake Biwa, central Japan. We determined the concentrations of 19 elements and the compositions of stable S and Sr isotopes in the main tributaries of the lake and compared them with the corresponding values obtained from the lake water during the circulation period. Results of a principal component analysis indicated that the components dissolved in the lower reaches of the tributaries can be divided into group 1 (HCO3, SO4, NO3, Ca, Mg, Sr) and group 2 components (Cl, Br, Na, K, Ba, Rb, Cs). The concentrations of group 1 components were high in the rivers of the southern area, which is urbanized and densely populated, and the eastern area, which consists of plains where agriculture predominates, compared with the rivers of the northern and western areas, which are mostly mountainous and sparsely populated. The concentrations of group 2 components tended to be high in the river water of industrial areas. The delta S-34 values of SO4 in the river water converged to 0 +/- 2 parts per thousand as the SO4 concentration increased and, excluding the areas where limestone is extensively distributed, as the HCO3 concentration increased. In particular, both the delta S-34 values (0 +/- 2 parts per thousand) and the Sr-87/Sr-86 ratios (0.7117 +/- 0.0005) fell within narrow ranges in the small and medium rivers of the eastern plain area, where rice is widely grown. These values agreed respectively with the delta S-34 values of the fertilizers used in the Lake Biwa basin and the soil-exchangeable Sr-87/Sr-86 in the eastern plain. The characteristics of water quality in the small and medium rivers of the eastern area can be explained by a model in which sulfuric, nitric, and bicarbonic acids generated by the decomposition of agricultural fertilizer and paddy rice selectively leached out alkaline-earth elements adsorbed on the soil and sediments of the plain or dissolved calcium carbonate enriched with Mg and Sr. Compared with tributary waters, the lake water was depleted in NO3, owing to denitrification, and in Mn, owing to mineralization, which occur under the redox condition of bottom sediments. Excluding NO3 and Mn, the compositions of both the dissolved elements and the Sr and S isotopes in the water of Lake Biwa can be approximately reproduced by simple mixing of the tributary water, indicating that these components provide effective indices for evaluating the relationship between the waters of the lake and its tributaries. (C) 2007 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.scitotenv.2007.08.042

大気圏核実験由来放射性炭素14を用いた生態学

陀安一郎, 兵藤不二夫, 石川尚人

生物の科学「遺伝」11月号 2008年

Divergence times in the termite genus Macrotermes (Isoptera : Termitidae)

R. Brandl, F. Hyodo, M. von Koff-Schmising, K. Maekawa, T. Miura, Y. Takematsu, T. Matsumoto, T. Abe, R. Bagine, M. Kaib

MOLECULAR PHYLOGENETICS AND EVOLUTION 45 ( 1 ) 239 - 250 2007年10月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ACADEMIC PRESS INC ELSEVIER SCIENCE

The evolution of fungus-growing termites is supposed to have started in the African rain forests with multiple invasions of semi-arid habitats as well as multiple invasions of the Oriental region. We used sequences of the mitochondrial Coll gene and Bayesian dating to investigate the time frame of the evolution of Macrotermes, an important genus of fungus-growing termites. We found that the genus Macrotermes consists of at least 6 distantly related clades. Furthermore, the Coll sequences suggested some cryptic diversity within the analysed African Macrotermes species. The dates calculated with the Coll data using a fossilized termite mound to calibrate the clock were in good agreement with dates calculated with COI sequences using the split between Locusta and Chortippus as calibration point which supports the consistency of the calibration points. The clades from the Oriental region dated back to the early Tertiary. These estimates of divergence times suggested that Macrotermes invaded Asia during periods with humid climates. For Africa, many speciation events predated the Pleistocene and fall in range of 6-23 million years ago. These estimates suggest that savannah-adapted African clades radiated with the spread of the semi-arid ecosystems during the Miocene. Apparently, events during the Pleistocene were of little importance for speciation within the genus Macrotermes. However, further investigations are necessary to increase the number of taxa for phylogenetic analysis. (c) 2007 Elsevier Inc. All rights reserved.

DOI： 10.1016/j.ympev.2007.07.007

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