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Lithosiini (Lepidoptera: Erebidae: Arctiinae) is distinctive in having some species that feed on lichens, whereas the majority of moths feed on vascular plants. However, the larval diet of most Lithosiini species is poorly known. This study examines whether Lithosiini species, collected in a tropical rainforest of Borneo (nine species) and a temperate forest of Japan (eight species), feed on lichens as larvae, based on stable isotope analyses. As a result, the δ¹⁵N values for eight of nine Lithosiini species collected from Borneo were notably lower than those of nine co-occurring herbivorous non-Lithosiini species, and were similar to those of sympatric, lichen-feeding termites; however, δ¹³C and δ¹⁵N values of one Lithosiini species (Adites sp.) were significantly higher than those of the other moth species and similar to those of humus-feeding termites and predatory insects occurring at the same site. These results have suggested that the Lithosiini in the Southeast Asian tropical rainforests contain some species that feed on lichens as their larval main diet and at least one species whose larvae feed on humus or animal-derived materials. In contrast, the δ¹³C and δ¹⁵N values of all examined Lithosiini species (eight species) in the temperate forest have suggested that their larvae fed on plants and not on lichens. Our stable isotope ratio analysis presented quantitative evidence suggesting lichen-feeding by Lithosiini moths in a tropical rainforest without observation of feeding behavior during the larval stages.

Topographic positions within a natural forest can considerably influence litter traits, soil microbial characteristics, and nitrogen (N) mineralization, causing plant–soil feedbacks. Despite the high abundance of coarse litter (woody debris and coarse roots) in forest ecosystems, most studies have focused on linkages between fine litter (leaves and fine roots) and N dynamics and/or the soil microbial community. We investigated the association of fine and coarse litter with soil microbial biomass, community structure, and N mineralization at upper and lower slope positions on sedimentary rocks in a temperate forest dominated by Fagus crenata. Greater coarse litter abundance and litter C-to-N ratio, and lower soil microbial biomass, bacterial abundance, and N mineralization potential were found in upper positions than in lower positions. Among litter traits, coarse litter abundance and litter C-to-N ratio were the best predictors of the microbial biomass and fungal-to-bacterial dominance, possibly due to differences in climatic stress among plant communities. Microbial traits were the best predictors of N mineralization potential. Fine litter traits and coarse litter abundance are likely linked to soil microbial characteristics and N mineralization in natural forests with variable topography.

This study quantified the numbers and sex ratio of adult Sericania hidana (Coleoptera: Scarabaeidae) in a subalpine forest in 2017. Data from an area littered with coarse woody debris (CWD) created by a typhoon in 1959 were compared with those from an area where CWD had been cleared by salvage logging. Three types of traps were used: flight interception traps (FITs) with a black light, pitfall traps (PITs), and soil emergence traps (SETs). Carbon and nitrogen stable isotopes were analyzed to evaluate S. hidana diets and habitats. Overall, there were more S. hidana in the unsalvaged sites than in the salvaged sites. The FITs captured only males but SETs captured both males and females. The SETs on CWD captured more S. hidana than did SETs on soil in both the salvaged and unsalvaged sites. The PITs captured only a few individuals; thus, PITs are not suitable for studying this insect, although such traps were previously reported to capture S. hidana adults. Stable isotope analyses suggested that S. hidana feeds on a variety of plant materials, including living plants and CWD. These results suggest that CWD has long‐term effects on insect populations. Soil emergence traps provide an effective method to quantitatively evaluate insect ecology, and FITs can effectively screen for the existence of insects.

The Osumi Strait and its neighboring waters are major spawning grounds for commercially important small pelagic and coastal fish in the Pacific coastal area of Japan. Mesopelagic fish larvae are also abundant here, co-occurring with the larvae of commercial species. However, it is unknown whether these fish groups compete for prey. We examined the diet of four commercial fish groups (Engraulis japonicus, Trachurus japonicus, Triglidae spp., and Sebastiscus spp.) and two mesopelagic species (Sigmops gracilis, Myctophum asperum) during their larval stages to determine whether they had the same prey source. Morphological analysis and DNA metabarcoding of gut contents showed that the main prey species of all six fish groups were calanoid copepods. However, results from metabarcoding differed greatly from morphological analysis, showing that appendicularians were abundant in the guts of S. gracilis, M. asperum, and Sebastiscus spp. This may be because the methods differ in how they determine prey composition, with morphological analysis relying on counts of identifiable prey parts and metabarcoding being only a semi-quantitative method. In addition, appendicularians might be underestimated by metabarcoding analysis due to variation in genome size, copy number of target genes, and primer mismatches. Stable isotope analysis supported the importance of appendicularians as prey for S. gracilis, M. asperum, and Sebastiscus spp. Our results indicate that the two mesopelagic species and Sebastiscus spp. may compete for prey, but E. japonicus, T. japonicus, and Triglidae spp. occupy niches different from those of the two mesopelagic species. Our results imply that the trophic pathway via appendicularians may support the feeding of dominant mesopelagic species and enable coexistence with commercial species in the study area.

The origin of ammonium-nitrogen in Indonesian coastal groundwater has not been intensively examined, meanwhile the elevated concentration remains a concern. This research aims at tracing the potential sources of ammonium-nitrogen in the groundwater of Indramayu, Indonesia where groundwater is vital for livelihood. From results, a combined examination of nitrogen isotope, coliform bacteria, land-use, and geology confirmed the natural and anthropogenic origins of ammonium-nitrogen in the groundwater. In the brackish-water aquaculture region, groundwater has &delta, 15NNH4 values from +1.8 to +4.8&permil, signifying that ammonium-nitrogen is derived from mineralization of organic nitrogen to ammonium. Furthermore, ammonium has a significantly positive relationship with sodium indicating the exchangeable ammonium is mobilized to groundwater via cation exchange. Meanwhile ammonium-nitrogen from anthropogenic waste was detected in agricultural and residential region. The groundwater has more varied &delta, 15NNH4 values, from &minus, 2.9 to +16.1&permil, which implies attenuation of ammonium-nitrogen from several sources namely manure, mineral fertilizer, sewage, and pit latrines. Also, the presence of E. coli confirms the indication of human and animal waste contamination. However, since ammonium has no relationship with sodium, cation exchange is not feasible and ammonium-nitrogen flows into the groundwater from anthropogenic sources along with liquid wastes.

The relative importance of topography and vegetation in shaping local soil invertebrate communities is poorly understood. We investigated changes in the species and trait compositions of Collembola communities associated with different topography and forest types. Our study sites encompassed various topographies with different slope aspects and forest types; specifically, natural deciduous broad-leaved forests and deciduous coniferous plantations in Japan. The body length and edaphic adaptation score, which are representative of a certain life-form, were used as Collembola traits. Across a topographic gradient from south to north-facing slopes, the total biomass of Collembola was higher in dry plots than in humid plots, and the forest types did not affect either abundance, biomass, or species diversity. Variation partitioning analysis revealed that topography played an important role in determining species composition and functional traits, whereas forest types and spatial distance had minor roles. The responses of community weighted mean traits (CWMs) to environmental change were more pronounced than those of species composition. The CWM and functional diversity of body length were higher in the dry plots than in the humid plots. These changes in traits might be explained by food supply or habitat structure increasing large individuals via topography, rather than by physical stress filtering out intolerant small individuals. These results suggest that slope topography is an important determinant of the Collembola community structure in cool-temperate forest ecosystems.

Accurate morphological ant mimicry by Myrmarachne jumping spiders confers strong protective benefits against predators. However, it has been hypothesized that the slender and constricted ant-like appearance imposes costs on the hunting ability because their jumping power to capture prey is obtained from hydraulic pressure in their bodies. This hypothesis remains to be sufficiently investigated. We compared the jumping and prey-capture abilities of seven Myrmarachne species and non-myrmecomorphic salticids collected from tropical forests in Malaysian Borneo and northeastern Thailand. We found that the mimics had significantly reduced abilities compared with the non-mimics. The analysis using geometric morphometric techniques revealed that the reduced abilities were strongly associated with the morphological traits for ant mimicry and relatively lower abilities were found in Myrmarachne species with a more narrowed form. These results support the hypothesis that the jumping ability to capture prey is constrained by the morphological mimicry and provide a new insight into understanding the evolutionary costs of accurate mimicry.

Ants are known to have various feeding habits and play important roles in many terrestrial ecosystems. However, little is known about how the feeding habits of each ant species are affected by the environmental changes associated with forest succession. In this study, we examined how feeding habits as well as the species composition and food preference of ants would respond to 105-year-old natural secondary succession of a cool-temperate forest. Stable carbon and nitrogen isotopes and radiocarbon were used to infer the feeding habits. The species richness was not affected by forest stand age. Redundancy analysis indicated that stand age, litter N concentration, and soil microbial respiration had significant relationships with the ant species composition. The bait experiments showed that honey bait became more attractive to ants relative to tuna bait in late succession. This was probably associated with changes in available food resources, such as nectar, during succession. Although the isotopic signatures differed significantly among the sample types (i.e., ant species, canopy leaves, and leaf litter), they were not significantly affected by forest stand age or by the interaction between sample types and stand age. This indicates that the ants showed consistent differences in feeding habits among the species during succession. Our results suggest that despite great changes in vegetation, each ant species would maintain functional roles in C and N flows during forest succession.

Myxomycetes are one of the major microbial predator groups found in detrital food webs within terrestrial ecosystems. They are typical inhabitants of coarse woody debris (CWD). However, the association between fungal communities and the foraging habits of myxomycetes has not been explored sufficiently in the field. Our study aimed to find community relationships between myxomycetes and fungi, a potential prey, on CWD, and the trophic status of saproxylic myxomycetes using stable isotope analysis of their sporocarps. Records of sporocarps present on 184 Pinus densiflora logs during a 3-year period listed 37 species of myxomycetes and 45 species of fungi. Ordination analysis using occurrence data of 34 dominant species (17 myxomycetes and 17 fungi) revealed their dynamic succession during log decay. Fungal dominants were clearly divided into two groups—earlier and later— and the majority of myxomycetes occurred during the middle stages of log decay between the first and second groups of fungal dominants. Species level associations between fungal and myxomycetes communities were rare. Isotopic nitrogen (δ15N) values of myxomycetes were significantly higher than those of wood-decay fungi, but few myxomycetes showed δ15N values higher than those of ectomycorrhizal fungi. Isotopic carbon (δ13C) values of myxomycetes were not significantly different from those of fungi. δ15N values of myxomycetes and fungi and δ13C of myxomycetes significantly increased with an increase in wood decay. However, these positive correlations between stable isotope profiles and wood decay disappeared after the values were calibrated by subtracting the δ15N and δ13C values of sapwood from those of myxomycetes and fungi. While saproxylic myxomycetes have long been assumed to be bacterivous, the results of this study suggest that wood-decay fungi could be an important part of their diet, and their foraging associations might be non-species specific.

Invasions are ecologically destructive and can threaten biodiversity. Trophic flexibility has been proposed as a mechanism facilitating invasion, with more flexible species better able to invade. The termite hunting needle ant Brachyponera chinensis was introduced from East Asia to the United States where it disrupts native ecosystems. We show that B. chinensis has expanded dietary breadth without shifting trophic position in its introduced range. Transect sampling of ants and termites revealed a negative correlation between the abundance of B. chinensis and the abundance of other ants in introduced populations, but this pattern was not as strong in the native range. Both termite and B. chinensis abundance were higher in the introduced range than in native range. Radiocarbon (14C) analysis revealed that B. chinensis has significantly younger ‘diet age’, the time lag between carbon fixation by photosynthesis and its use by the consumer, in the introduced range than in the native range, while stable isotope analyses showed no change. These results suggest that in the introduced range B. chinensis remains a termite predator but also feeds on other consumer invertebrates with younger diet ages such as herbivorous insects. Radiocarbon analysis allowed us to elucidate cryptic dietary change associated with invasion success., 海を渡った日本のアリが米国の森を襲う --放射性炭素分析で明らかになった食性幅の拡大--. 京都大学プレスリリース. 2017-11-15.

Native tree species are frequently unable to effectively grow in non-native tree cultivation scenarios. In the Loess Plateau, China, it is difficult to find native oak (Quercus liaotungensis) seedlings in non-native black locust forests. Black locust is an arbuscular mycorrhizal (AM) tree, but oak is an ectomycorrhizal (ECM) tree. Plants highly depend on their symbiotic mycorrhizal fungi to take up water, nitrogen (N) and other nutrients. We hypothesized that black locust forests would not provide ECM inoculum to oak seedlings, limiting their water and nutrient uptake, which would be improved by ECM inoculum. Here, we (1) sowed seeds, with or without oak forest soils, (2) transplanted seedlings collected in oak forests, with or without oak forest soils, and (3) planted seedlings germinated in autoclaved or unautoclaved oak forest soils. We measured the survival and growth rate for all three experiments, along with chemical properties, and root ECM colonization. Oak seeds sowed with oak forest soils had higher mycorrhizal colonization, leaf N concentrations and survival rate, and lower root δ13C than the seeds sowed without oak forest soils. Planting with oak forest soils also increased the survival rate of the germinated seedlings, but not the transplanted seedlings. Overall, our study suggested that the use of oak forest soils in the black locust forest to improve the water and N uptake of oak seedlings by providing the ECM inoculum, resulting in a high survival rate. Our study also implies that the method of sowing seeds was effortless and effectively compared to transplanting wild/nursery seedlings.

Lignins have been used as a biomarker to explore changes in terrestrial organic matter input into lakes and to investigate past watershed vegetation. Burial of organic carbon (OC) in lake sediments, an important component of the global C cycle, is likely associated with the terrestrial OC input. However, few studies have explored changes in terrestrial C input into lakes in the last century. Furthermore, the relationship between lignin phenol compositions and watershed vegetation remains poorly examined. In this study, we examined changes in OC concentrations, OC mass accumulation rates (MAR), and lignin phenol compositions over the last century in sediments from six lakes in Japan that differ in watershed land-use and vegetation. The sediments were dated using 210 Pb and 137 Cs, and showed increased OC concentrations and MARs in three lowland lakes over the last century. This pattern was not found in three mountain lakes. In one of the lowland lakes, lignin phenol concentrations normalized to OC did not change during the periods with high OC concentrations and MARs. This indicates that not only eutrophication but also enhanced terrestrial OC input could lead to greater burial of OC. The lignin phenol compositions did not show clear trends over the last century in most of the lakes examined. The ratios of syringyl to vanillyl phenols and the lignin phenol vegetation index had significant relationships with proportions of angiosperms in watershed vegetation. These results demonstrate that lignin phenols are useful in inferring recent as well as past changes in lake watershed environments.

Volcanic deposits increase soil organic carbon storage. However, little is known about the effect of volcanic deposits on forest soil nitrogen (N) dynamics and microbial communities. We explored gross and net N transformation rates and microbial community structure using a phospholipid fatty acid (PLFA) method across eight forests with soils derived from different parent material in Japan. Volcanic mineral soils had approximately three-fold greater total N and inorganic N contents and gross nitrification, ammonium immobilization, and nitrate immobilization rates that were one order of magnitude higher than in non-volcanic soils. Moreover, volcanic mineral soils had a 1.7-fold lower N turnover rate, which was estimated as net N mineralization rate per soil N. This was likely caused by a higher gross N immobilization rate, potentially due to the mineral traits of volcanic soils. Volcanic mineral soils had approximately four- and three-fold greater microbial biomass-N and bacterial PLFA contents, respectively, and the fungal:bacterial PLFA ratio was lower in volcanic mineral soils than in non-volcanic soils. Microbial community structure, analyzed using non-metric multidimensional scaling, was distinct between volcanic and non-volcanic soils, and was significantly affected by soil characteristics. This study demonstrates that aside from soil carbon storage, volcanic deposits are related to increases in soil N immobilization, N content, bacterial biomass, and N transformation rates in forest ecosystems.

Primary forests are known to have positive effects on the biodiversity of surrounding secondary forests. However, it is unclear whether primary forest remnants affect the feeding habits of consumers that inhabit secondary forests. Here, we examined whether the feeding habits of ants (Formicidae: Hymenoptera) belonging to four taxonomic groups ( Camponotus gigas , Odontomachus rixosus , Pachycondyla spp., and Polyrhachis spp.) differed in Macaranga secondary forests with different proportions of surrounding primary forest remnants in Sarawak, Malaysia. In the secondary forests, our previous study showed that species diversity of ants significantly increased as the proportion of surrounding primary forest remnants increased. We explored feeding habits by measuring carbon and nitrogen isotope ratios (δ 13 C and δ 15 N). We also estimated the diet age of the ants, which represents the lag time between primary production and utilization by ants, by performing radiocarbon (Δ 14 C) measurements. δ 13 C of ants and litter decreased with the increase in primary forest remnants, likely indicating a more closed canopy cover around the sites. Meanwhile, baseline-corrected δ 15 N of ants, which considered the variation in plant δ 15 N among study sites, or diet ages of the ants did not show significant response to the proportion of the surrounding primary forest remnants. δ 13 C, δ 15 N, and diet ages showed consistent differences among the ant taxa across different proportions of primary forest remnants. These isotopic patterns suggest that, in contrast to the effect on species diversity, surrounding primary forest remnants did not markedly affect the feeding habits of the ants that persisted in the secondary forests.

The soil microbial community and nitrogen (N) dynamics change seasonally due to several factors. The microbial community structure (MCS) can regulate N dynamics. However, there is insufficient information on seasonal changes in MCS and the relationship between MCS and N dynamics. We investigated MCS and N dynamics in forest soils with two different fertilities throughout a year. MCS, measured with phospholipid fatty acid (PLFA) analysis, showed a consistent seasonal trend, regardless of the fertility. Microbial indices (particularly the Saturated-/monounsaturated-PLFA ratio; Sat/mono) indicated a major PLFA shift among seasons, with temperature likely the most important factor. The fungal-/bacterial-PLFA ratio in the dormant season (December–April) was approximately 1.3 times greater than in the growing season (June–November). The trend in N dynamics showed that in summer (June–August), the gross N mineralization potential was greater than immobilization, whereas in winter (December–April), immobilization was dominant. The net mineralization potential in the growing season was approximately 1.6 times higher than in the dormant season. Moreover, a relationship was found between Sat/mono and N transformation potentials. We highlight the microbial sensitivity to seasonal dynamics which can be associated with temperature, as well as carbon and N dynamics.

Insects are the most diverse organisms and often the most abundant animals in some ecosystems. Despite the importance of their functional roles and of the knowledge for conservation, the trophic ecology of many insect species is not fully understood. In this review, I present how stable carbon (C) and nitrogen (N) isotopes have been used to reveal the trophic ecology of insects over the last 30 years. The isotopic studies on insects have used differences in C isotope ratios between C3 and C4 plants, along vertical profiles of temperate and tropical forest stands, and between terrestrial and aquatic resources. These differences enable exploration of the relative importance of the food resources, as well as movement and dispersal of insects across habitats. The 13C-enrichment (approximately 3‰) caused by saprotrophic fungi can allow the estimation of the importance of fungi in insect diets. Stable N isotopes have revealed food resource partitioning across diverse insect species above and belowground. Detritivorous insects often show a large trophic enrichment in 13C (up to 3‰) and 15N (up to 10‰) relative to the food substrates, soil organic matter. These values are greater than those commonly used for estimation of trophic level. This enrichment likely reflects the prevalence of soil microbial processes, such as fungal development and humification, influencing the isotopic signatures of diets in detritivores. Isotope analysis can become an essential tool in the exploration of insect trophic ecology in terms of biogeochemical C and N cycles, including trophic interactions, plant physiological and soil microbial processes.

Summary Energy and material flows from dead organic matter, or detritus, to generalist predators have a potential impact on the food web dynamics. However, little is known about how commonly generalist predators depend on detritivorous prey, or the detritus on which the detritivores have fed in terrestrial food webs. To examine this, we measured the diet ages of terrestrial invertebrate and vertebrate consumers (>30 species) at multiple trophic levels in a tropical rain forest, with a particular focus on ants and termites by using radiocarbon (14C). Here, we defined diet age as the lag time between the primary production and the utilization by consumer organisms. The diet ages varied from 0 to >50 years and corresponded to known feeding habits of the consumers. Herbivores such as bees, butterflies, a frugivorous bird and bat, and nectar-feeding ants had young diet ages (0–3 years). Meanwhile, detritivores such as termites had old diet ages, which increased according to the food resources in the order of litter (6 years), soil (10 years) and wood (≥19 years). The diet ages of predators such as wolf spiders, hunting wasps, army ants, tree shrews and an insectivorous bat were intermediate (2–8 years), indicating the dependence of many predators on detritivores. Because known dietary components of the predators include herbivores and detritivores, the intermediate ages likely indicate the coupling of energy and material flows between plant-based and detritus-based food webs. Diet ages of soil-feeding termite and army ant differed significantly, although a previous study reported that their nitrogen isotope ratios were indistinguishable despite the differing feeding habits. This indicates that radiocarbon can distinguish the two factors, trophic enrichment and the below-ground processes (humification), both of which could influence the nitrogen isotopic signatures of the terrestrial consumers. Our results show that radiocarbon would provide insights into structures of terrestrial food webs as well as time frame of energy and material flows through the webs.

Forest development in temperate regions is considered to be a global carbon sink. Many studies have examined forest development after harvesting or fire from aboveground (e.g., biomass) or belowground (e.g., soil nutrient) perspectives. However, few studies have explored forest development from both perspectives simultaneously in cool-temperate forests in Japan. In this study, we examined changes over 105 years in both aboveground and belowground components during secondary natural succession. The aboveground biomass increased for 50 years and reached a plateau in a 105-year-old stand. The N mineralization rate increased during succession for 50 years, but showed a decline in the 105-year-old stand due to the decrease in the nitrification rate in late succession. The percent nitrification (i.e., relative contribution of nitrification to N mineralization) decreased significantly with increasing forest stand age. The N mineralization rates had significant relationships with N concentrations of the dominant tree foliage and litter fall and with the amount of litter fall N. Meanwhile, other belowground properties (i.e., soil pH, phenol concentration, soil microbial respiration, and litter mass loss) did not show any significant relationship with forest stand age. This may be because the soil at the study sites was heterogeneous and consisted of Cambisols and Andosols, the latter of which originally has high organic matter content, and thus may have buffered the effect of the aboveground development. These results indicate that belowground N dynamics are more closely associated with aboveground development than other belowground properties in these forests.

We review the use of stable carbon isotope ratios (δ13C) and radiocarbon natural abundances (Δ14C) for stream food web studies. The δ13C value of primary producers (e.g., periphytic algae, hereafter periphyton) in streams is controlled by isotopic fractionation during photosynthesis and variable δ13C of dissolved CO2. When periphyton δ13C differs from that of terrestrial primary producers, the relative contribution of autochthony and allochthony to stream food webs can be calculated. Moreover, the variation in periphyton δ13C can reveal how much stream consumers rely on local resources because each stream habitat (e.g., riffle vs. pool, open vs. shaded) usually has a distinctive δ13C. However, periphyton δ13C often overlaps with that of terrestrial organic matter. On the other hand, periphyton Δ14C is less variable than δ13C among habitats, and reflects the Δ14C of dissolved CO2, which could be a mixture of “aged” (Δ14C 0 ‰) carbon. This is because the Δ14C is corrected by its δ13C value for the isotopic fractionation during photosynthesis. Recent studies and our data indicate that many stream food webs are supported by “aged” carbon derived from the watershed via autochthonous production. The combined use of δ13C and Δ14C allows robust estimation of the carbon transfer pathway in a stream food web at multiple spatial scales ranging from the stream habitat level (e.g., riffle and pool) to watershed level (autochthony and allochthony). Furthermore, the Δ14C of stream food webs will expand our understanding about the time frame of carbon cycles in the watersheds.

Tropical landscape structures have been transformed into mosaic structures consisting of small patches of primary and secondary forests, and areas of other land use. Diversity of insect assemblages is often higher in primary forests than in surrounding secondary forests. However, little is known about how the primary forests affect diversity in surrounding secondary forests in a landscape. In Sarawak, Malaysia, the typical landscape in areas from which lowland tropical rainforests had originally spread consists mainly of primary and secondary forests, with small areas of cultivation. In this study, we examined how the proportion of remnant primary forests in a landscape affects species diversity and species composition of ants and dung beetles in Macaranga-dominated secondary forests. The proportions were quantified based on remote-sensing data at various spatial scales, ranging from 100- to 5,000-m radius from each of the target forests. We found that the proportions of remnant primary forests within a 100-m radius had a significant positive effect on ant species diversity, and those within 100-, 300-, and 500-m radii significantly affected species compositions. However, the proportions of remnant primary forests had no significant relationship with dung beetle diversity, while those within 100- and 1,000-m radii had significant effects on species composition. The different responses to the remnant primary forests are likely to be related to differences in the movement and dispersal traits between the two taxa.

The globalization of food production and distribution has homogenized human dietary patterns irrespective of geography, but it is uncertain how far this homogenization has progressed. This study investigated the carbon and nitrogen isotope ratios in the scalp hair of 1305 contemporary Japanese and found values of -19. 4 ± 0. 6‰ and 9. 4 ± 0. 6‰ (mean ± SD), respectively. Within Japan, the inter-regional differences for both isotope ratios was less than 1‰, which indicates low dietary heterogeneity among prefectural divisions. The carbon and nitrogen isotope ratios of the hair showed a significant correlation with the results of questionnaires on self-reported dietary habits. The carbon isotope ratios from Japan were lower than those in samples from the USA but higher than those in samples from Europe. These differences stem from the varying dietary proportions of food products originally derived from C3 and C4 plants. The dietary variation of Japan is as small as those of Europe and USA and smaller than those of some Asian countries. These results indicate that dietary homogeneity has progressed in Japan, which may indicate the influence from the spread of the Western-style diet and food globalization, although dietary heterogeneity among countries is still preserved., 現代日本人の均質な食生活 ―髪の毛の安定同位体分析から―. 京都大学プレスリリース. 2016-09-20.

A new species of the genus Castoponera Deeleman-Reinhold, 2001, Castoponera christae sp. n., is described here. The species is closely related to Castoponera lecythus Deeleman-Reinhold, 2001, but can be distinguished by the structures of the male palp and the female genitalia.

Nitrogen (N) and carbon (C) isotopic signatures (δ15N and δ13C) serve as powerful tools for understanding temporal changes in ecosystem processes, but how these signatures change across boreal forest chronosequences is poorly understood. The δ15N, δ13C, and C/N ratio of foliage of eight dominant plant species, including trees, understory shrubs, and a moss, as well as humus, were examined across a 361 years fire-driven chronosequence in boreal forest in northern Sweden. The δ13C and C/N ratio of plants and humus increased along the chronosequence, suggesting increasing plant stress through N limitation. Despite increasing biological N fixation by cyanobacteria associated with feather mosses, δ15N showed an overall decline, and δ15N of the feather moss and associated vascular plants diverged over time from that of atmospheric N2. Across this chronosequence the N fixed by cyanobacteria is unlikely to be used by mosses and vascular plants without first undergoing mineralization and mycorrhizal transport, which would cause a change in δ15N signature due to isotopic fractionation. The decreasing trend of δ15N suggests that as the chronosequence proceeds, the plants may become more dependent on N transferred from mycorrhizal fungi or from N deposition.

Most theories attempting to explain the coexistence of species in local communities make fundamental assumptions regarding whether neighbors exhibit competitive, neutral, or positive resource-use interactions; however, few long-term data from naturally assembled plant communities exist to test these assumptions. We utilized a 13-year experiment consisting of factorial removal of three shrub species (Vaccinium myrtillus, V. vitis-idaea, and Empetrum hermaphroditum) and factorial removal of two functional groups (tree roots and feather mosses) to assess how neighbors affect N acquisition and growth of each of the three shrub species. The removal plots were established on each of 30 lake islands in northern Sweden that form a natural gradient of resource availability. We tested the hypotheses that: (1) the presence of functionally similar neighbors would reduce shrub N acquisition through competition for a shared N resource; (2) the removal of functional groups would affect shrub N acquisition by altering the breadth of their niches; and (3) soil fertility would influence the effects of neighbor removals. We found that the removal of functionally similar neighbors (i.e., other shrub species) usually resulted in higher biomass and biomass N, with the strength of these effects varying strongly with site fertility. Shrub species removals never resulted in altered stable N isotope ratios (delta(15)N), suggesting that the niche breadth of the three shrubs was unaffected by the presence of neighboring shrub species. In the functional group removal experiment, we found positive effects of feather moss removal on V. myrtillus biomass and biomass N, and negative effects on E. hermaphrotium N concentration and V. vitis-idaea biomass and biomass N. Tree root removal also caused a significant shift in foliar delta(15)N of V. myrtillus and altered the delta(15)N, biomass, and biomass N of E. hermaphroditum. Collectively, these results show that the resource acquisition and niche breadth of the three shrub species are often affected by neighbors, and further that both the identity of neighbors and site fertility strongly determine whether these interactions are positive, negative, or neutral. These findings have implications for understanding species coexistence and the reciprocal relationships between productivity and species diversity in this ecosystem.

MAKI NOGUCHI AITA1,2*, KAZUAKI TADOKORO3, NANAKO O. OGAWA4, FUJIO HYODO5, REIICHIRO ISHII1, S. LAN SMITH1, TOSHIRO SAINO1, MICHIO J. KISHI1,6, SEI-ICHI SAITOH6 AND EITARO WADA1,4 1 RESEARCH INSTITUTE FOR GLOBAL CHANGE, JAPAN AGENCY FOR MARINE-EARTH SCIENCE AND TECHNOLOGY (JAMSTEC), 3173-25 SHOWA-MACHI, KANAZAWAKU, YOKOHAMA, KANAGAWA, 236-0001, JAPAN, GRADUATE SCHOOL OF FISHERIES SCIENCES, HOKKAIDO UNIVERSITY, 3-1-1 MINATO-MACHI, HAKODATE, HOKKAIDO, 041-8611, JAPAN, TOHOKU NATIONAL FISHERIES RESEARCH INSTITUTE, FISHERIES RESEARCH AGENCY (FRA), SHIOGAMA, 3-27-5 SHINHAMA-CHO, SHIOGAMA, MIYAGI 985-0001, JAPAN, INSTITUTE OF BIOGEOSCIENCES, JAPAN AGENCY FOR MARINE-EARTH SCIENCE AND TECHNOLOGY (JAMSTEC), 2-15 NATSUSHIMA-CHO, YOKOSUKA, KANAGAWA 237-0061, JAPAN, RESEARCH CORE FOR INTERDISCIPLINARY SCIENCES, OKAYAMA UNIVERSITY, 3-1-1, TSUSHIMANAKA, KITA-KU, OKAYAMA, 700-8530, JAPAN AND FACULTY OF FISHERIES SCIENCES, HOKKAIDO UNIVERSITY, 3-1-1 MINATO-MACHI, HAKODATE, HOKKAIDO 041-8611, JAPAN

The stable nitrogen (N) isotope ratio (δ15N) has been used to examine the anthropogenic N input (i.e., septic water, wastewater, and manure) to aquatic ecosystems, because anthropogenic N generally has a δ15N signature distinct from that found in nature. Aquatic organisms and the derived organic matter such as sediments are reported to become increasingly enriched in 15N as the human population density increases in watersheds. However, little is known about the relationship in steppe ecosystems, where the livestock population is greater than that of humans. Here, we conducted a preliminary study in the Selenga river mainstream watershed in Mongolia, which covers an area of approximately 300,000 km2. A multiple regression analysis revealed that the δ15N of the riverine sediment was significantly affected by the human population density and more significantly by livestock population density. The population density, including both humans and livestock, significantly influenced δ15N of the macrophytic Potamogeton spp. The results showed that δ15N of riverine organic matter can be an indicator of the human and livestock population density, which is likely associated with the status of N cycles in livestock-dominated watersheds.

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 (δ15N and δ13C) of hymenopterans (12 families, ≥16 genera and ≥32 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 δ15N and δ13C 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 δ15N 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 δ15N values of wasps varied greatly from −0.1‰ (Braconidae sp.) to 8.6‰ (Bembix sp.), suggesting that their feeding habits also range from omnivory to predation. The ant species Camponotus gigas had δ13C 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 δ15N and δ13C 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.

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 approximately 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.

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。

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 Inariyama) 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.

Carbon and nitrogen stable isotope ratios (δ13C and δ15N) 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 δ13C values are similar (