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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.

Nitrogen (N) is an essential plant nutrient, and plants can take up N from several sources, including via mycorrhizal fungal associations. The N uptake patterns of understory plants may vary beneath different types of overstory trees, especially through the difference in their type of mycorrhizal association (arbuscular mycorrhizal, AM; or ectomycorrhizal, ECM), because soil mycorrhizal community and N availability differ beneath AM (non-ECM) and ECM overstory trees (e.g., relatively low nitrate content beneath ECM overstory trees). To test this hypothesis, we examined six co-existing AM-symbiotic understory tree species common beneath both AM-symbiotic black locust (non-ECM) and ECM-symbiotic oak trees of dryland forests in China. We measured AM fungal community composition of roots and natural abundance stable isotopic composition of N (δ15N) in plant leaves, roots, and soils. The root mycorrhizal community composition of understory trees did not significantly differ between beneath non-ECM and ECM overstory trees, although some OTUs more frequently appeared beneath non-ECM trees. Understory trees beneath non-ECM overstory trees had similar δ15N values in leaves and soil nitrate, suggesting that they took up most of their nitrogen as nitrate. Beneath ECM overstory trees, understory trees had consistently lower leaf than root δ15N, suggesting they depended on mycorrhizal fungi for N acquisition since mycorrhizal fungi transfer isotopically light N to host plants. Additionally, leaf N concentrations in the understory trees were lower beneath ECM than the non-ECM overstory trees. Our results show that, without large differences in root mycorrhizal community, the N uptake patterns of understory trees vary between beneath different overstory trees.

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 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.

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.

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.

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 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 δ13C and δ15N 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 δ13C and δ15N of the consumers differed significantly among the trophic groups. The predators had significantly higher δ13C than the herbivores, and were similar in δ13C to the detritivores, suggesting that most predators examined depend largely on below-ground food webs. δ15N was higher in predators than detritivores by about 3‰. The comparison of δ13C in plant materials and herbivores suggests that most herbivores are dependent on C fixed in the canopy layers. The vertebrates had significantly higher δ15N and δ13C 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.

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 4I 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 4I 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 4I individuals, suggesting a higher proportion of immigrants among the former.

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.

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.

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 (δ15N) 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 δ15N 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.

We analyzed stable carbon and nitrogen isotope ratios in a sample of human and nonhuman mammal bones excavated from the Yoshigo and Inariyama shell mounds of the Late-Final Jomon pe- riods in Aichi Prefecture, Japan, with a view to determining individual dietary differences. To inves- tigate possible reasons for the dietary variations identified, we related isotope ratios to sex and tooth ablation patterns. At both sites, large intra-site variations in δ 13 C and δ 15 N values were found, com- pared with other Jomon populations previously studied, suggesting higher than usual levels of dietary variability, and at both sites there was a positive correlation between δ 13 C and δ 15 N values. The diet of the Jomon people at both these sites had two main protein sources: marine (marine finfish and shell- fish) and terrestrial (C3 plants and terrestrial mammals) protein. The intra-site variability is probably explained by consumption of these resources in different proportions. Analysis of the Yoshigo shell mound data indicated that sex is one of the factors determining dietary difference. It was also found that individual differences in diet in Yoshigo males are greater than in females. This pattern was re- peated in the Inariyama shell mound data. Dietary differences were found to be related to ritual tooth ablation characteristics, particularly in males. At Inariyama, type 4I ritual tooth ablation was associated with comparatively greater dependency on terrestrial resources, while type 2C tooth ablation was as- sociated with greater dependency on marine resources. This may indicate that type 4I males engaged predominantly in hunting, and type 2C males in fishing, as a means of food acquisition. These results are possibly the earliest evidence of occupational differentiation in the Jomon people.

The degradation of tropical forests is progressing rapidly and its ecological effects on wild animals are a global concern. We evaluated the hypothesis that small mammals in highly degraded forest occupy higher trophic levels than those in somewhat degraded forests, as indicated by diets high in consumers such as insects, in a tropical rain forest in Sarawak, Malaysia. After correcting for differences in the δ15N values for primary production among the study sites, the δ15Ncorrected values for rats and mice (Muridae) differed significantly among forest types. Rats and mice in more degraded forest had higher δ15Ncorrected values than those in less degraded or primary forest; in contrast, treeshrews (Tupaiidae) and squirrels (Sciuridae) showed no significant differences in the δ15Ncorrected values among forest types. We found significant positive correlations between canopy openness and the δ15Ncorrected values for one species of squirrel and two species of rats. This hypothesis was supported for small mammals that have normal dietary preferences for plants, i.e., omnivorous rodents, but not for those that normally prefer insects, i.e., treeshrews. The δ15N values for omnivorous mammals may be useful as an indicator of changes in food-web structure in response to forest disturbance.

Summary 1We propose that diets of consumers in a food web have various ages, where age is defined as the time elapsed since carbon (C) in the diet was fixed from atmospheric CO2 by primary producers. To examine the diet ages for primary consumers in a detrital food web, we measured the radiocarbon (14C) content of termites collected in Thailand in 1998 and 2004. Diet ages were estimated by comparing the 14C content of samples with records of atmospheric 14CO2, which doubled in the early 1960s as a result of nuclear weapons tests and decreased after the nuclear test ban treaty. For comparison, we measured the 14C content of bees as primary consumers in a grazing web at the same study site. Stable carbon and nitrogen (N) isotope ratios were also analysed. 2The 14C contents of the same species of termites decreased during the sampling interval, indicating that they used organic matter produced after the peak in atmospheric 14CO2. The diet ages were estimated to be 12–18, 7–13 and 5–9 years for the wood-feeder (Microcerotermes crassus), the soil-feeders (Dicuspiditermes makhamensis and Termes comis) and the fungus-grower (Macrotermes carbonarius), respectively. One colony of soil-feeder (T. comis), which nested in a fallen tree trunk, had exceptionally low 14C content, and its diet age was estimated to be around 50 years. The two bee species had lower 14C contents compared with the termites, and their diet ages were estimated to be 0 (Apis florea) and 2–4 years (Trigona sp.). 3Stable C and N isotope ratios of termites showed similar patterns as previously reported, and no clear difference was observed between 1998 and 2004. Although the bees and the fungus-growing termite had similar stable C and N isotope ratios, their diet ages differed. 4Our study suggests that radiocarbon can be used to estimate the diet ages of consumers in terrestrial food webs. Diet age should provide new insight into the trophic positions of organisms in grazing and detrital food webs and the interactions between these two webs.

We examined the crown architecture of two canopy species, Fagus crenata Blume, which is highly shade tolerant, and Quercus crispula Blume, which is less shade tolerant, in upper and lower positions on a slope in a cool-temperate forest in Japan. The purpose of this study was to investigate the relative effects of the competitive position for the light environment and developmental constraints on the crown architecture of two species that have different degrees of shade tolerance. In both species, the maximum attainable height was smaller on the upper slope than on the lower slope. The light environment brightened with increasing tree height. Trees in similar competitive position and thus similar light environments were shorter on the upper slope than on the lower slope. When we considered tree height relative to the maximum attainable height, the difference between the upper and lower slopes in the relationship of competitive position to tree height disappeared. Thus, relative tree height was a good index of the competitive position for the light environment when the trees of both slope positions were pooled. The relationships of crown depth and width to relative tree height differed between trees on the upper and lower slopes, while the relationships of crown depth and width to actual tree height were similar. This suggests that developmental constraints are more important than the competitive position in determining the crown architecture of the two species. However, variation in crown architecture was greater in Q. crispula than in F. crenata , probably because of the difference in shade tolerance between the two species.

Summary 1To investigate whether the role of symbiotic fungi in lignin degradation and food provision differs among fungus-growing termites (four species of Macrotermes, three species of Odontotermes, Hypotermes makhamensis, Ancistrotermes pakistanicus and Pseudacanthotermes militaris), the chemical composition of fungus combs of different ages and the chitinolytic activity in the gut of termites were analysed. In addition, the carbon stable isotope ratios (δ13C) in old combs, worker termite tissues and fungal nodules (aggregated conidia) were compared. 2In Macrotermes spp., the carbohydrate : lignin ratio of the combs increased with increased comb age, but it decreased or remained the same in Odontotermes spp., H. makhamensis, A. pakistanicus and P. militaris. In contrast, the chitin : carbohydrate ratio and ash content increased more over time in the combs of Odontotermes spp., H. makhamensis, A. pakistanicus and P. militaris than in the combs of Macrotermes spp. 3Chitinolytic activity in the gut of workers was higher in O. takensis, H. makhamensis and A. pakistanicus than in M. annandalei. 4In all species examined, the δ13C value increased in the sequence: old combs < termites < fungal nodules. Based on a two-source model of δ13C, the contribution of fungi to termite nutrition was considered higher in Odontotermes spp., H. makhamensis, A. pakistanicus and P. militaris than in Macrotermes spp. 5These results suggest that symbiotic fungi play different roles among fungus-growing termites. In Macrotermes spp., the main role of symbiotic fungi is to degrade lignin, so that the termites can utilize cellulose more efficiently, whereas in Odontotermes spp., H. makhamensis, A. pakistanicus and P. militaris, it is to serve as a food source.

1. Nitrogen and carbon isotope ratios and uric acid concentrations in fungus-growing termites (Isoptera: Termitidae: Macrotermitinae), sampled in Cameroon and Thailand, were determined in order to compare castes that are known to differ in behaviour and feeding habits. 2. Nitrogen isotope ratios (δ15N) were either not significantly changed or lower in workers compared with the diet (the fungus combs), whereas carbon isotope ratios (δ13C) were higher in worker termites than in the fungus combs. 3. In old workers, δ15N values were unexpectedly low and correlated negatively with whole-body uric acid concentrations. This indicates that older workers retain uric acid, which has a low δ15N value, to conserve nitrogen within the colony and, furthermore, that older colony members may ultimately be consumed by younger conspecifics.

Tissue N and C stable isotope ratios of two sympatric termite species were investigated in relation to those of their stored food materials at two savanna sites in north-eastern Australia (Woodstock and Oak Valley). At both sites, the δ 15 N values of termite tissues and the stored food materials of the litter-feeding species Amitermes laurensis were significantly greater than their equivalents in the grass-harvesting species Drepanotermes rubriceps . In addition, the carbohydrate/lignin and C/N ratios were higher and chitin/carbohydrate ratios were lower in food materials stored in the mounds of D. rubriceps . Both sets of analyses confirmed that D. rubriceps assimilates less decomposed food materials than A. laurensis . Tissue δ 13 C values indicated that both species assimilated similar proportions of C3 and C4 plant materials at the Woodstock site, but that the workers of A. laurensis assimilated a greater proportion of C3 plant material at the Oak Valley site. The δ 15 N values of termites from the Woodstock site were significantly greater than those from Oak Valley, although the differences in order at each site were consistent between species. The results indicate that N and C stable isotope ratios must be carefully compared across habitats.

Stable (δ13C and δ15N) and radio- (14C, 137Cs and 210Pb) isotopes were determined for termites that have been sampled from a dry evergreen forest in Thailand. A wood-feeding termite, Microcerotermes crassus, was separated from soil-feeders: Termes propinquus, Termes comis and Dicuspiditermes makhamensis by δ13C and δ15N values. The Termes group in Thailand had less diverse values in δ13C and δ15N than those in Australia, where the feeding habits of the ‘Termes’ group are more diverse. Other soil-feeding termites produced similar δ13C values, but a larger range in δ15N values. 14C-percent modern carbon (pMC) values suggest that the soil-feeding termites used younger carbon than the wood-feeding termites, and this was consistent with the termites from Cameroon, central Africa. Values of δ13C and 14C-pMC indicate that surface soil was used by a soil-feeding termite, D. makhamensis, in making the nest mounds, and deeper soil (10–30 cm) by a fungus-growing termite, Macrotermes carbonarius. 210Pb and 137Cs were scarcely incorporated into the termites, although 214Pb was recovered from the workers. The results suggest that stable- and radioisotopes are useful in the study of detritivorous animals, organic matter decomposition and ecosystem engineering.

In order to investigate the role of the mutualistic fungus, Termitomyces sp., in the fungus-growing termite, Macrotermes gilvus , we applied CP/MAS 13 C NMR and selected proximate analyses to fungus comb of different ages and degrees of maturation. We found evidence that lignin degradation took place progressively in the fungus comb. In vitro digestibility of cellulose in old fungus comb, on which the termites feed, was approximately 3-fold higher than that in the fresh part. These results confirm the ‘lignin degradation hypothesis’ that the role of the mutualistic fungi is to degrade lignin and enhance the digestibility of cellulose for the termites, suggesting the ability of the termite–fungus association to make extremely efficient use of plant material.

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.

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-15 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-15, 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 CO2 by photosynthesis; it was estimated by comparing the radiocarbon (C-14) content of these organisms to atmospheric (CO2)-C-14 records. 3. Stable N isotope ratios increased along the humification gradient of diets, and values for earthworms and termites varied from 1.8 parts per thousand to 9.9 parts per thousand and from -1.5 parts per thousand to 15.9 parts per thousand, 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-15 with the humification of below-ground diets should be considered when interpreting stable N isotope ratios of terrestrial food webs.

Pycnotarsobrentus inuiae Maruyama & Bartolozzi, gen. nov. and sp. nov. (Brentinae: Eremoxenini) is described from the Lambir Hills National Park, Borneo (Sarawak, Malaysia) based on specimens collected from Crematogaster difformis F. Smith, 1857 ant nests in the myrmecophytic epiphytic ferns Platycerium crustacea Copel. and Lecanopteris ridleyi H. Christ. A second species of Pycnotarsobrentus is known from Malaysia but is represented by only one female and consequently not yet described pending discovery of a male. Pycnotarsobrentus belongs to the tribe Eremoxenini and shares some character states with the African genus Pericordus Kolbe, 1883. No species of Eremoxenini with similar morphological modifications are known from the Oriental region.