Stable isotope analysis of modern human hair collected from Asia (China,India, Mongolia,and Pakistan)

We report isotopic data (δ²H, δ¹⁸O n = 196; δ¹³C, δ¹⁵N n = 142; δ³⁴S n = 85) from human hair and drinking water (δ²H, δ¹⁸O n = 67) collected across China, India, Mongolia, and Pakistan. Hair isotope ratios reflected the large environmental isotopic gradients and dietary differences. Geographic information was recorded in H and O and to a lesser extent, S isotopes. H and O data were entered into a recently developed model describing the relationship between the H and O isotope composition of human hair and drinking water in modern USA and pre‐globalized populations. This has anthropological and forensic applications including reconstructing environment and diet in modern and ancient human hair. However, it has not been applied to a modern population outside of the USA, where we expect different diet. Relationships between H and O isotope ratios in drinking water and hair of modern human populations in Asia were different to both modern USA and pre‐globalized populations. However, the Asian dataset was closer to the modern USA than to pre‐globalized populations. Model parameters suggested slightly higher consumption of locally producedfoods in our sampled population than modern USA residents, but lower than pre‐globalized populations. The degree of in vivo amino acid synthesis was comparable to both the modern USA and pre‐globalized populations. C isotope ratios reflected the predominantly C₃‐based regional agriculture and C₄ consumption in northernChina. C, N, and S isotope ratios supported marine food consumption in some coastal locales. N isotope ratios suggested a relatively low consumption of animal‐derived products compared to western populations. Am J Phys Anthropol 2010. © 2009 Wiley‐Liss, Inc.     

Understanding the ecology of mammalian carnivorans and herbivores from Valdegoba cave (Burgos, northern Spain) through stable isotope analysis

Stable carbon and oxygen isotope analyses of mammalian carnivoran and herbivore species from the late Pleistocene Valdegoba cave site in northern Spain imply competition and partitioning in resource use. In general, the data support the previously recognized ecology for the analyzed species. δ¹³C values show that the ecosystem around the cave was dominated by C₃ plants. The observed δ¹⁸O values are similar to what is found in modern environments. The analyzed bovids, Bos primigenius, Capra pyrenaica, and Rupicapra rupicapra, showed the most positive δ¹³C values. Bos primigenius had the most positive mean carbon isotope value and is suggested to feed on grasses in open environments. Values for Capra pyrenaica primarily indicate grass feeding, while Rupicapra rupicapra had the widest diet for the analyzed species, likely including grass and browse. Cervus elaphus, Equus ferus, Equus hydruntinus, and Stephanorhinus hemitoechus displayed more negative δ¹³C values indicating the use of similar resources. The smallest species analyzed, Castor fiber, displayed the most negative δ¹³C and δ¹⁸O values, implying a preference for eating C₃ plants and being semi-aquatic. The canids, Canis lupus and Vulpes vulpes, displayed the most positive δ¹³C and δ¹⁸O values, and overlap many of the sampled ungulate species. Positive δ¹⁸O values in canids implies that this group obtains much of its water from its prey, uses a different water source, or has physiological differences from the other carnivorans that influence oxygen isotope values. Lynx pardinus had values similar to the canids. Crocuta crocuta had δ¹³C values more negative than expected for a generalist predator. These values are likely due to concentration of diet on taxa from more forested environments. The most negative δ¹³C values are observed in the bears, Ursus arctos and Ursus spelaeus. These values are the likely result of hibernation and the inclusion of significant vegetation in bear diets.     

Trophic level delineation and resource partitioning in a South African afromontane forest bird community using carbon and nitrogen stable isotopes

Southern African forests are naturally fragmented yet hold a disproportionately high number of bird species. Carbon and nitrogen stable isotopes were measured in feathers from birds captured at Woodbush (n = 27 species), a large afromontane forest in the eastern escarpment of Limpopo province, South Africa. The δ¹³C signatures of a range of forest plants were measured to categorise the food base. Most plants sampled, including two of five grass species, had δ¹³C signatures typical of a C₃ photosynthetic pathway (?29.5 ± 1.9‰). Three grass species had a C₄ signature (?12.0 ± 0.6‰). Most bird species had δ¹³C values representing a predominantly C₃‐based diet (?24.8‰ to ?20.7‰). δ¹⁵N values were as expected, with higher levels of enrichment associated with a greater proportion of dietary animal matter. The cohesive isotopic niche defining most species (n = 22), where the ranges for δ¹³C and δ¹⁵N were 2.4‰ and 3.4‰, respectively, highlight the difficulties in understanding diets of birds in a predominantly C₃‐based ecosystem using carbon and nitrogen stable isotopes. However, variation in isotopic values between and within species provides insight into possible niche width and the use of resources by different birds within a forest environment.     

Host range determination in a novel outbreak pest of sugarcane,Cacosceles newmannii (Coleoptera: Cerambycidae,Prioninae), inferred from stable isotopes

1. An outbreak of Cacosceles newmannii (Coleoptera: Cerambycidae) was detected for the first time on sugarcane (Saccharum spp.) in 2015 in KwaZulu-Natal, South Africa. Although primary host plants of this native species remain unknown, these are central to testing hypotheses concerning the outbreak.
2. We hypothesized that this species has undergone a host plant shift (i.e. a feeding association with a novel host plant).
3. We compared δ¹³C and δ¹⁵N ratios of adult beetles retrieved from South African museum collections, collected between 1891 and 2016 (n = 23; ‘pre-outbreak’), with samples from infested fields in 2017 (n = 9, ‘post-outbreak’) and in 2019 (n = 23, ‘post-outbreak’), as well as diverse, plausible host plants (n = 42 samples across 10 species) from infested fields and surrounding patches of indigenous and commercial forest vegetation. We used Bayesian isotope mixing models to infer the relative contribution of the different plants to the diet of C. newmannii.
4. Pre-outbreak, C₃ plants contributed strongly to the larval diet, whereas post-outbreak, C₄ plants were the largest component of their diet. There was some indication of C₄ plants contributing to their diet pre-outbreak.
5. Our results suggest that the outbreak of this polyphagous beetle was not a dramatic host shift but rather a rapid increase in the proportion of C₄ plants already in their diet.
6. We concluded that plants from the families Fabaceae and Poaceae are the most likely host plants of this species. Nevertheless, the drivers of this rapid outbreak on sugarcane remain poorly determined and should be the focus of future research.

     

Records of palaeo‐seawater condition from oxygen‐isotope profiles of early Pleistocene fossil molluscs from the Seoguipo Formation (Korea)

Kim, J.K., Khim, B.‐K., Woo, K.S., & Yoon, S.H. 2009: Records of palaeo‐seawater condition from oxygen‐isotope profiles of early Pleistocene fossil molluscs from the Seoguipo Formation (Korea). Lethaia, Vol. 43, pp. 170–181. High‐resolution δ¹⁸O profiles of early Pleistocene fossil molluscs (Mizuhopecten tokyoensis hokurikuensis) from the shallow‐marine sedimentary Seoguipo Formation (Korea) were found to exhibit distinct annual cycles identified by their unique seasonality (δ¹⁸O amplitude). A direct comparison of fossil δ¹⁸O profiles with that of living shells (Amusium japonicum japonicumi) indicated that the palaeoseawater conditions differed from present‐day seawater. Specifically, the positive δ¹⁸O shift in the isotope profile of the fossil specimens relative to that of the living mollusc shell reflected that palaeotemperature was lower than that today. However, a comparison of the coldest palaeotemperatures (determined from the heaviest δ¹⁸O values of fossil shells), with the present‐day winter temperatures indicates that temperature variation alone cannot account for the entire positive δ¹⁸O offset. These findings indicate that variation in the seawater δ¹⁸O_w values plays a dominant role in the biogenic carbonate precipitation of fossils. Thus, the fossil shells obtained from stratigraphic units suggest different palaeoenvironmental conditions, including lower temperatures and ¹⁸O‐enriched glacial seawater, when compared with the present‐day conditions. The Seoguipo Formation records at least five cycles of relative sea‐level fluctuations, with changes in fossil δ¹⁸O amplitudes separated by sequence boundaries likely to reflect variations of unique palaeoseawater condition, although the oxygen‐isotope profile of fossil molluscs appears to provide a snap‐shot of the palaeoclimatic signature. □Early Pleistocene, mollusc fossils, oxygen isotope, palaeoenvironment, seawater temperature.     

The evolution of ecological specialization in southern African ungulates: competition‐ or physical environmental turnover?

Using long‐term diet reconstructions spanning the past one million years, we contrast hypotheses that biotic interactions versus physical environmental changes are primary drivers of evolutionary turnover in mammals. We use stable carbon (δ¹³C) and oxygen (δ¹⁸O) isotope ratios in tooth enamel carbonate to trace herbivore niche shifts through the Late Quaternary Land Mammal Ages (LMAs) of grassland savannas in the South African interior (Cornelian‐1.0 to 0.6 Ma; Florisian‐500 to 10 ka; and Holocene/modern). Data reveal niche separation amongst closely related coeval taxa, and dispersals through time into empty niche spaces following extinctions. This suggests a primary role of competitive exclusion and niche displacement for speciation and extinctions in these early grassland environments. However, niche changes through time show a similar trend in many taxa, entailing increased δ¹³C (elevated C₄ grass consumption) from the Cornelian to the Florisian, and from the Florisian to the Holocene/modern, and elevated δ¹⁸O in Holocene/modern taxa that reflect global aridification around the terminal Pleistocene. Commonality in isotopic trends implies universal environmental forcing of ecological, and ultimately macroevolutionary, turnover. Yet some taxa shift from a mixed C₃/C₄ diet in the Florisian to a near‐pure C₃ diet today. Indeed, we find that while δ¹³C data are normally distributed for Cornelian fossils, non‐normal distributions characterize more recent time intervals. Such distributions are in line with the bimodal distribution of δ¹³C and diet in contemporary African ungulates. Thus, while environmental forcing did not, by necessity, lead to increases in C₄ intake, the results show changes from mixed to more specialized diets. We propose that this niche specialization was a function of long‐term exposure to C₄ grasslands, consistent with predictions that relatively high metabolic demands of C₄ grazing in subtropical environments forced the differentiation of herbivores into one of two highly specialized feeding niches, i.e. C₃ browsing or C₄ grazing.     

Isotopic reconstruction of human diet and animal husbandry practices during the Classical-Hellenistic, imperial, and Byzantine periods at Sagalassos, Turkey

An isotopic reconstruction of human dietary patterns and livestock management practices (herding, grazing, foddering, etc.) is presented here from the sites of Düzen Tepe and Sagalassos in southwestern Turkey. Carbon and nitrogen stable isotope ratios were determined from bone collagen extracted from humans (n = 49) and animals (n = 454) from five distinct time periods: Classical‐Hellenistic (400–200 BC), Early to Middle Imperial (25 BC–300 AD), Late Imperial (300–450 AD), Early Byzantine (450–600 AD), and Middle Byzantine (800–1200 AD). The humans had protein sources that were based on C₃ plants and terrestrial animals. During the Classical‐Hellenistic period, all of the domestic animals had δ¹³C and δ¹⁵N signatures that clustered together; evidence that the animals were herded in the same area or kept in enclosures and fed on similar foods. The diachronic analysis of the isotopic trends in the dogs, cattle, pigs, sheep, and goats highlighted subtle but distinct variations in these animals. The δ¹³C values of the dogs and cattle increased (reflecting C₄ plant consumption) during the Imperial and Byzantine periods, but the pigs and the goats displayed little change and a constant C₃ plant‐based diet. The sheep had a variable δ¹³C pattern reflecting periods of greater and lesser consumption of C₄ plants in the diet. In addition, the δ¹⁵N values of the dogs, pigs, cattle, and sheep increase substantially from the Classical‐Hellenistic to the Imperial periods reflecting a possible increase in protein consumption, but the goats showed a decrease. Finally, these isotopic results are discussed in the context of zooarcheological, archeobotanical, and trace element evidence. Am J Phys Anthropol 149:157–171, 2012. © Wiley Periodicals, Inc.     

Stable forest–savanna mosaic in north‐western Tanzania: local‐scale evidence from δ13C signatures and 14C ages of soil fractions

Aim The spatio‐temporal dynamics of dry evergreen forest patches in the savanna biome of the Kagera region (north‐western Tanzania) are largely unknown owing to a lack of pollen and macrofossil evidence. Our aims were to reconstruct local‐scale shifts of the forest–savanna boundary in order to determine whether the forests have been expanding or retreating on a centennial and millennial time‐scale. Location The Kagera region of north‐western Tanzania, East Africa. Methods The vegetation reconstruction was based on analysing δ¹³C signatures in soils along a transect spanning both C₄ open savanna and C₃ forest vegetation. Furthermore, we fractionated soil organic matter (SOM) according to density and chemical stability to analyse δ¹³C values of soil fractions with distinct radiocarbon ages. Results We found sharp changes in δ¹³C signatures in bulk SOM from the forest to the savanna, within a few metres along the transect. The forest soil profiles carried a persistent C₃‐dominated signature. Radiocarbon dating of the oldest, most recalcitrant forest soil fraction yielded a mean age of 5500 cal. yr bp , demonstrating that the forest has existed since at least the mid‐Holocene. The savanna sites showed a typical C₄ isotopic signature in SOM of topsoils, but subsoils and more recalcitrant SOM fractions also contained signals of C₃ plants. The dense soil fraction (ρ > 1.6 g cm^?3) carrying a pure C₄ label had a mean age of c. 1200 cal. yr bp , indicating the minimum duration of the dominance of grass vegetation on the savanna site. At the forest edge, the older C₄ grass signature of SOM has steadily been replaced by the more negative δ¹³C fingerprint of the forest trees. As this replacement has occurred mainly in the 10‐m‐wide forest–savanna ecotone over the last c. 1200 years, the forest expansion must be very slow and is very likely less than 15 m century^?1. Main conclusions Our results suggest that forest patches in the Kagera savanna landscape are very stable vegetation formations which have persisted for millennia. During the last millennium, they have been expanding very slowly into the surrounding savanna at a rate of less than 15 m century^?1.     

Modern macaque dietary heterogeneity assessed using stable isotope analysis of hair and bone

Dietary variability might have been a major factor in the dispersal and subsequent persistence of the genus Macaca in both tropical and temperate areas. Macaques are found from northern Africa to Japan, yet there have been few systematic attempts to compare diets between different modern populations. Here we have taken a direct approach and sampled museum-curated tissues (hair and bone) of Macaca mulatta (rhesus macaques) for carbon and nitrogen stable isotope dietary analyses. Samples from India, Vietnam, and Burma (Myanmar) were taken, representing both tropical and temperate populations. The δ¹³C values obtained from hair show that the temperate macaques, particularly those from Uttar Pradesh, have a δ¹³C signature that indicates at least some use of C₄ resources, while the tropical individuals have a C₃-based diet. However, δ¹³C values from bone bioapatite indicate a C₃-based diet for all specimens and they do not show the C₄ usage seen in the hair of some animals, possibly because bone represents a much longer turnover period than that of hair. The results of δ¹⁵N analyses grouped animals by geographic region of origin, which may be related to local soil nitrogen values. The greatest variation in δ¹⁵N values was seen in the specimens from Burma, which may be partly due to seasonality, as specimens were collected at different times of year. We also investigated the relationship between the hair, bone collagen, and bone bioapatite δ¹³C results, and found that they are highly correlated, and that one tissue can be used to extrapolate results for another. However, our results also suggest that hair may pick up discrete feeding traces (such as seasonal usage), which are lost when only bone collagen and bioapatite are examined. This has important implications for dietary reconstructions of archaeological and paleontological populations.     

Ancient latitudinal gradients of C3/C4 grasses interpreted from stable isotopes of New World Pleistocene horse (Equus) teeth

Carbon and oxygen isotopic data are reported from 116 Pleistocene Equus teeth from sixty-six localities in the New World ranging from 68°N (Alaska, Canada) to 35°S (Argentina). Equus species have been predominantly grazers, and as such, carbon isotopic values of their tooth enamel provide evidence of the Pleistocene distribution of C₃ and C₄ grasses. The carbon data presented here indicate a gradient (δ¹³C range of 10 parts/mil) in the relative proportion of C₃ and C₄ grasses between high latitude and equatorial Equus samples. The largest amount of change from C₃ to C₄ grasses during the Pleistocene occurred in the mid-latitudes between about 30 to 40°. The oxygen data, which vary proportionately with temperature, indicate a latitudinal gradient (δ¹⁸O range of 20 parts/mil) between high-latitude and equatorial Equus samples. The basic pattern of latitudinal gradients of C₃/C₄ grass distribution and temperature as interpreted from these Pleistocene data is similar to the modern-day. The use of stable isotopes of fossil herbivore teeth represents a new means to interpret Pleistocene climates and terrestrial ecology.     

Trophic structure and major trophic links in conventional versus organic farming systems as indicated by carbon stable isotope ratios of fatty acids

Using bulk tissue and fatty acid ¹³C analysis we investigated major trophic pathways from soil microorganisms to microbial consumers to predators in conventional versus organic farming systems planted for the first time with maize. Organic farming led to an increase in microbial biomass in particular that of fungi as indicated by phospholipid fatty acids (PLFAs). Microbial PLFAs reflected the conversion from C₃ to C₄ plants by a shift in δ¹³C of 2‰, whereas the isotopic signal in fatty acids (FAs) of Collembola was much more pronounced. In the euedaphic Protaphorura fimata the δ¹³C values in maize fields exceeded that in C₃ (soybean) fields by up to 10‰, indicating a close relationship between diet and vegetation cover. In the epedaphic Orchesella villosaδ¹³C values shifted by 4‰, suggesting a wider food spectrum including carbon of former C₃ crop residues. Differences in δ¹³C of corresponding FAs in consumers and resources were assessed to assign food web links. P. fimata was suggested as root and fungal feeder in soybean fields, fungal feeder in conventional and leaf consumer in organically managed maize fields. O. villosa likely fed on root and bacteria under soybean, and bacteria and fungi under maize. Comparison of δ¹³C values in FAs of the cursorial spider Pardosaagrestis and O. villosa implied the latter as important prey species in soybean fields. In contrast, the web‐building spider Mangora acalypha showed no predator–prey relationship with Collembola. The determination of δ¹³C values in trophic biomarker FAs allowed detailed insight into the structure of the decomposer food web and identified diet‐shifts in both consumers at the base of the food web and in top predators in organic versus conventional agricultural systems. The results indicate changes in major trophic links and therefore carbon flux through the food web by conversion of conventional into organic farming systems.     

Reliability of δ13C and δ15N in faeces for reconstructing savanna herbivore diet

We tested the reliability of herbivore faecal δ¹³C and δ¹⁵N values for reconstructing diet through review of an extensive database derived from a 3-year study of ungulates in South Africa's Kruger National Park. Faeces are a useful material for stable isotope studies of diet because they record dietary turnover at very short time scales, and because sampling is non-invasive. However, the validity of faecal isotope proxies may be questioned because they represent only undigested food remains. Results from Kruger Park confirm that free-ranging browsers have faecal δ¹³C consistent with C₃ feeding, grazer faeces are C₄, and mixed-feeder faeces intermediate. Although the respective ranges do not overlap, there is significant variation in faecal δ¹³C of browsers and grazers (～2.0–4.0‰) across space and through time. We demonstrate that most (～70%) of this variation can be ascribed to corresponding patterns of variation in the δ¹³C of C₃ and C₄ plants, respectively, re-enforcing the fidelity of faecal isotope proxies for diet but highlighting a need for mixing models that control for variations in plant δ¹³C in order to achieve accurate diet reconstructions. Predictions for the effects of climate (rainfall) and ecophysiology on ¹⁵N-abundance variations in mammals do not persist in faeces. Rather, faecal δ¹⁵N tracks changes in plant δ¹⁵N, with further fractionation occurring primarily due to variations in dietary protein (reflected by %N). Controlling for these effects, we show that a dual-isotope multiple source mixing model (Isosource) can extend diet reconstructions for African savanna herbivores beyond simplified C₃/C₄ distinctions, although further understanding of variations in mammal δ¹⁵N are needed for greater confidence in this approach.     

Tracking dietary habits of cave arthropods associated with deposits of hematophagous bat guano: A study from a neotropical savanna

Carbon and nitrogen stable isotopes were used to track major dietary variations in arthropods found in a cave located in a neotropical savanna in Central Brazil. We determined the δ¹³C and δ¹⁵N for cave crickets, cockroaches, spiders, guano of a hematophagous bat, and leaf litter found on the ground near the cave entrance. The δ¹³C and δ¹⁵N for the cricket and cockroaches showed that bat guano was not the only food item for these arthropods. They had intermediate δ¹³C and δ¹⁵N between bat guano and leaf litter, which means that they consumed additional food resources other than guano in their diet, independent of distribution of guano deposits in the cave. The spiders, predators with great mobility, seemed to not have a preferential diet item since their isotope signals indicated they hunt both crickets and cockroaches. The δ¹³C of the bat guano (?15.4‰) indicated that the diet of these hematophagous bats relied on animals fed with C₄ plants. The conversion of native savanna vegetation of which the debris is mostly from C₃ plants, to pasture, based on C₄ African grass, a remarkably common land use transformation in the region, is indirectly influencing the diet of hematophagous bats, which basically relied on exotic fauna. The C and N stable isotope ratios showed that the arthropods inside the cave do not rely solely on bat guano for their diet, but interact directly with the external environment, through litter debris, indicating a significant exchange of energy and matter between the cave environment and the surrounding area.     

Kangaroo tooth enamel oxygen and carbon isotope variation on a latitudinal transect in southern Australia: implications for palaeoenvironmental reconstruction

Tooth enamel apatite carbonate carbon and oxygen isotope ratios of modern kangaroos (Macropus spp.) collected on a 900-km latitudinal transect spanning a C₃–C₄ transition zone were analysed to create a reference set for palaeoenvironmental reconstruction in southern Australia. The carbon isotope composition of enamel carbonate reflects the proportional intake of C₃ and C₄ vegetation, and its oxygen isotope composition reflects that of ingested water. Tooth enamel forms incrementally, recording dietary and environmental changes during mineralisation. Analyses show only weak correlations between climate records and latitudinal changes in δ¹³C and δ¹⁸O. No species achieved the δ¹³C values (~?1.0 ‰) expected for 100 % C₄ grazing diets; kangaroos at low latitudes that are classified as feeding primarily on C₄ grasses (grazers) have δ¹³C of up to ?3.5 ‰. In these areas, δ¹³C below ?12 ‰ suggests a 100 % C₃ grass and/or leafy plant (browse) diet while animals from higher latitude have lower δ¹³C. Animals from semi-arid areas have δ¹⁸O of 34–40 ‰, while grazers from temperate areas have lower values (~28–30 ‰). Three patterns with implications for palaeoenvironmental reconstruction emerge: (1) all species in semi-arid areas regularly browse to supplement limited grass resources; (2) all species within an environmental zone have similar carbon and oxygen isotope compositions, meaning data from different kangaroo species can be pooled for palaeoenvironmental investigations; (3) relatively small regional environmental differences can be distinguished when δ¹³C and δ¹⁸O data are used together. These data demonstrate that diet–isotope and climate–isotope relationships should be evaluated in modern ecosystems before application to the regional fossil record.     

Diet, residential origin, and pathology at Machu Picchu, Peru

Pathological conditions in human skeletal remains provide a wealth of information about archaeological populations, but many are limited in their interpretive significance by their nonspecific etiologies. This study analyzes three common pathological conditions known to manifest in infancy and childhood in the skeletal population from Machu Picchu, Peru (N = 74) with published carbon, nitrogen, oxygen, strontium, and lead isotopic data (Turner et al.: J Archaeol Sci 36 (2009) 317–332; Turner et al.: Chungara: Revista de Antropología Chilena 42 (2010) 515–524) to distinguish early‐life diet from residential origins as significantly associated with pathologies among the site's inhabitants. Analyses of variance indicate highly significant variation between enamel δ¹⁸O values, which serve as a rough proxy of local environment, and both cribra orbitalia (CO) and porotic hyperostosis (PH), generally understood to be markers of anemia. Results tentatively suggest that individuals manifesting these lesions may have lived closer to the arid coasts; however, no significant variation was found in parameters of diet (enamel δ¹³C_carbonate, dentin δ¹³C_collagen, dentin δ¹⁵N) by either CO or PH, suggesting that the primary factors causing anemia may have been more significantly related to residential origin rather than diet. Linear enamel hypoplasia (LEH) frequency significantly varied by both dietary and residential parameters, supporting models of LEH formation from a synergy of dietary and environmental factors. These results support previous research on the etiology of PH in the Andes; they also represent a useful approach to refining site‐specific interpretations of pathological conditions in archaeological populations, and exploring etiological variation between populations. Am J Phys Anthropol, 2012. © 2012 Wiley Periodicals, Inc.     

Estimation of food composition of Hodotermes mossambicus (Isoptera: Hodotermitidae) based on observations and stable carbon isotope ratios

Abstract The diet of the harvester termite Hodotermes mossambicus was investigated at two sites with distinct dietary components: C₄ grasses (δ¹³C isotope values, ?13.8‰ to ?14.0‰) and C₃ plants (δ¹³C isotope values, ?25.6‰ to ?27.1‰). By comparing observations of food items carried into the colony by the termites and carbon isotope ratios of whole termites (that determined assimilated carbon), the relative proportion of the C₃ and C₄ plant food components of the termite diet was estimated. There was agreement between the observational data and stable carbon isotopic data, with grass representing approximately 93% of the diet of H. mossambicus at two study sites (urban and rural) on the South African highveld. However, when correcting for mass of food items, that is, C₃ and C₄, carried by termites, the proportion of grass (C₄) in the diet may be underestimated.     

Strengthening of the East Asian summer monsoon revealed by a shift in seasonal patterns in diet and climate after 2-3 Ma in northwest China

To examine climate variability in northwest China in the late Cenozoic and to test hypotheses regarding the development of C₄ ecosystems and the dynamics of the Asian monsoons, the carbon and oxygen isotopic compositions of 32 bulk and 368 serial tooth enamel samples from herbivores in the Linxia Basin (Gansu Province), ranging in age from 25 Ma to the present, were determined. The results corroborate and improve the record previously obtained from the area, showing that all mammals in the Linxia Basin lived in habitats consisting primarily of C₃ vegetation prior to 2-3 Ma and that C₄ grasses did not become a significant component of local ecosystems until the Quaternary. The data also show that shifts in climate to drier and/or warmer conditions after about 14, 9.5, 7, and 2.5 Ma, as indicated by positive δ¹⁸O excursions in the bulk enamel-δ¹⁸O record, were accompanied by increased seasonality; whereas negative δ¹⁸O shifts in the bulk data after about 11, 6, and 1.2 Ma, which indicate shifts to wetter and/or cooler climate, were associated with decreases in seasonality. Intra-tooth δ¹³C and δ¹⁸O profiles reveal significant changes in the seasonal patterns of diet and climate after ~ 2-3 Ma. Prior to ~ 2-3 Ma, there was little or no seasonal variation in herbivores' diets and all herbivores fed on C₃ vegetation year around. After that time, the data show a significant seasonal variation in the diets of horses and bovids, ranging from a pure C₃ to a mixed C₃/C₄ diet (with C₄ plants accounting for up to ~ 60% of the diet). An inverse relationship (or negative correlation) between δ¹³C and δ¹⁸O values within individual teeth — a pattern characteristic of the summer monsoon regime — is observed in younger (< 2-3 Ma) horses and bovids but not in older fossils. These changes in intra-tooth isotopic patterns provide strong evidence for an enhanced monsoon climate since about 2-3 Ma.     

Dietary and environmental reconstruction with stable isotope analyses of herbivore tooth enamel from the Miocene locality of Fort Ternan, Kenya

Tooth enamel of nine Middle Miocene mammalian herbivores from Fort Ternan, Kenya, was analyzed for δ¹³C and δ¹⁸O. The δ¹⁸O values of the tooth enamel compared with pedogenic and diagenetic carbonate confirm the use of stable isotope analysis of fossil tooth enamel as a paleoenvironmental indicator. Furthermore, the δ¹⁸O of tooth enamel indicates differences in water sources between some of the mammals. The δ¹³C values of tooth enamel ranged from −8·6–−13·0‰ which is compatible with a pure C₃diet, though the possibility of a small C₄fraction in the diet of a few of the specimens sampled is not precluded. The carbon isotopic data do not support environmental reconstructions of a Serengeti-typed wooded grassland with a significant proportion of C₄grasses. This study does not preclude the presence of C₃grasses at Fort Ternan; it is possible that C₃grasses could have had a wider geographic range if atmospheric CO₂levels were higher than the present values.     

Stable Isotope Evidence of Puma concolor (Felidae) Feeding Patterns in Agricultural Landscapes in Southeastern Brazil

We evaluated puma (Puma concolor) feeding patterns in southeastern Brazilian agricultural landscapes using carbon and nitrogen stable isotope analyses of hair collected from fecal samples (N = 64). We classified the samples into three groups: feeding patterns based on forest remnants, on the agricultural matrix or both. We observed a predominance of consumption of C₃ prey (~47% of individuals) in the area with the highest proportion of forest coverage. Conversely, C₄ prey were highly consumed (~40% of individuals) where the agricultural matrix was predominant. The δ¹³C values for pumas in both areas indicated that their food resources come from both forest remnants and the agricultural matrix and that some individuals preferentially consumed C₄ prey, indicating that food resources from the agricultural matrix make up most of their diet (~46% of prey individuals). The wide range of puma's δ¹⁵N values in both areas indicated a diet based on different types of prey. However, the C₄ group had higher values, indicating that both pumas and their prey feed on enriched resources from the agricultural matrix. The results confirm the high behavioral plasticity of pumas in using highly anthropogenic habitats. The stable isotope analyses conducted in this study yielded new information on large carnivore trophic ecology that might be useful in the development of new conservation strategies in disturbed areas.     

Paleoenvironmental reconstruction of the Asbole fauna (Busidima Formation, Afar, Ethiopia) using stable isotopes

The Middle Pleistocene environmental and climatic conditions at Asbole, lower Awash Valley, Ethiopia were reconstructed using stable carbon and oxygen isotopic composition (¹³C, ¹⁸O) of fossil tooth enamel coupled with faunal abundance data. We analyzed the isotopic composition of a total of 80 herbivorous tooth enamel samples from 15 mammalian taxa, which archive the dietary preferences and drinking behavior from the “Asbole faunal zone”. The carbon isotopic data signify a wide range of foraging strategies, across the entire spectrum of pure C4 to C4-dominated diet, mixed C3/C4 diet and C3-dominated diet. The oxygen isotopic enrichment between evaporation sensitive and insensitive taxa (?_ES-EI) is 3.7‰ which provides an estimate of the mean annual water deficit of the Middle Pleistocene at Asbole of 1470 mm, a value characteristic of modern arid landscapes in this part of the Awash Valley. The isotopic data coupled with faunal abundance data indicate an arid C4-dominated open-vegetated region, with an abundance of forest-dwelling primates that identify the presence of gallery forests flanking tributary streams to the paleo-Awash River. Thus, with these combined methodologies, it is possible to explicate a more detailed character of the “mosaic” of environments characteristic of Neogene savanna ecosystems. These findings, clearly indicate the importance of avoiding oversimplification of Pleistocene environmental reconstructions, based on single proxies at isolated localities.