Strontium isotopes track female dispersal in Taï chimpanzees

OBJECTIVES

Chimpanzees (Pan troglodytes) are patrilocal, with males remaining in their natal community and females dispersing when they reach sexual maturity. However, the details of female chimpanzee dispersal, such as their possible origin, are difficult to assess, even in habituated communities. This study investigates the utility of 87Sr/86Sr analysis for (1) assessing Sr baseline differences between chimpanzee territories and (2) identifying the status (immigrant or natal) of females of unknown origin within the territories of five neighboring communities in Taï National Park (Côte d'Ivoire).

MATERIALS AND METHODS

To create a local Sr isoscape for the Taï Chimpanzee Project (TCP) study area, we sampled environmental samples from TCP-established territories (n = 35). To assess dispersal patterns, 34 tooth enamel samples (one per individual) were selected from the Taï chimpanzee skeletal collection. 87Sr/86Sr analysis was performed on all 69 samples at the W.M. Keck Lab. The theoretical density and overlap of chimpanzee communities as well as generalized linear mixed models (GLMMs) were used to test each question.

RESULTS

87Sr/86Sr ratios for natal male chimpanzees ranged from 0.71662 to 0.72187, which is well within the corresponding environmental baseline range of 0.70774-0.73460. The local Sr isoscapes fit was estimated with the root-mean-square error value, which was 0.0048 (22% of the whole 87Sr/86Sr data range). GLMMs identified significant differences in 87Sr/86Sr ratios between natal and unknown North community origin groups, suggesting that after 1980, females of unknown origin could be immigrants to North community (n = 7, z-ratio = -4.08, p = 0.0001, power = 0.94).

DISCUSSION

This study indicates that 87Sr/86This study indicates that 87Sr/86Sr analysis can successfully identify immigrant females in skeletal collections obtained from wild chimpanzee communities, enabling the tracking of female dispersal patterns historically. There are, however, significant limitations within the scope of this study, such as (1) the absence of reliable maps for the TCP study area, (2) limited capacity for environmental sampling, (3) small sample sizes, and (4) tooth formation in wild chimpanzees.

Pastoralism and Emergent Complex Settlement in the Middle Bronze Age, Azerbaijan: isotopic analyses of mobility strategies in transformation

OBJECTIVES

This article explores the scale and seasonal patterns of mobility at the complex settlement site of Qızqala during the Middle Bronze Age (2400-1,500 BCE). By integrating human bone, teeth, and environmental samples this research tests the hypothesis of the persistent importance of community-wide seasonal pastoral transhumance during the early formation of complex settlement systems of the South Caucasus.

METHODS

This research applies stable oxygen and radiogenic strontium isotope analyses on incremental samples of human tooth enamel, bulk tooth enamel, and bone to resolve mobility patterns. Sequential and bulk sampling techniques elucidate seasonal and residential mobility behaviors. Extensive environmental isotope samples of plant and water were collected through regional survey and establish local and regional isotopic baselines, which are compared to human isotope analysis results.

RESULTS

Qızqala individuals exhibit low isotopic variability compared to regional contemporaries. ⁸⁷ Sr/⁸⁶ Sr ratios from human remains indicate seasonal and residential isotopic variability within the baseline ranges of local landscapes. δ¹⁸ O values display erratic patterns, but correspond to seasonal variability with fluctuations between highland and lowland altitudinal zone baseline values.

CONCLUSIONS

Results suggest that isotopic analysis of multiple elements and sequential enamel samples offers finer resolution on the complexities of human mobility strategies and elucidate the daily lives of often overlooked mobile populations. Higher resolution of individual mobility reveals shared routine behaviors that underscore the importance of diverse social collaborations in forming complex polities in the South Caucasus.

Intra- and inter-individual variability of stable strontium isotope ratios in hard and soft body tissues of pigs

RATIONALE

Stable isotope analysis has become an indispensable tool for the identification of the flow of matter in ecological sciences. Stable strontium isotope ratios are used in several different scientific fields as markers for provenance, mobility, and migration. A crucial prerequisite for such studies is a reliable definition of local ranges and an estimation of expected isotopic variability.

METHODS

To study the local variability of stable strontium isotope ratios at a specific place, a farrow of ecologically and locally grown pigs was investigated and strontium was extracted from their hard tissues (tooth enamel, bones and bristles) as well as soft tissues (meat, organs and blood) via dry- and wet-ashing procedures and subsequent column separation. The ⁸⁷ Sr/⁸⁶ Sr ratio was then measured via TIMS (thermal ionization mass spectrometry).

RESULTS

Reliable ⁸⁷ Sr/⁸⁶ Sr data was generated from all tissue types. Both intra- and inter-individual variability was high and tissue-specific patterns could be identified. High ranges occurred in sample types which were analyzed for animals of different age (pigs as well as piglets): teeth, parietal, mandible, femur, and leg muscle as well as in jaw muscle samples, which were only analyzed in adult pigs. Tooth enamel data showed a tooth-type-dependent pattern.

CONCLUSIONS

We conclude that a time factor played a role for the observed variability, e.g. a shift in food supply. Furthermore, we presume that local range estimates from the literature only work for tissues which integrate all consumed components over a sufficient amount of time and average fluctuations which can be found in tissues with higher turnover rates.

Manganese and Mn/Ca ratios in soil and vegetation in forests across the northeastern US: Insights on spatial Mn enrichment

Manganese (Mn) cycling in the Critical Zone is important because of its role as an essential nutrient and potential toxicity to plants and organisms. Quantifying Mn enrichment in terrestrial environments has been limited since Mn is monoisotopic. However, elemental ratios of Mn/Ca ratios may be used to determine spatial Mn enrichment and in aboveground and belowground pools. The objectives of this study were to quantify the spatial variation in Mn concentrations and Mn/Ca ratios in foliage, bolewood, forest floor, and mineral soil horizons across the northeastern United States and compare Mn/Ca ratios to estimate enrichment. Forest floor and mineral soil samples were collected from 26 study sites across the northeastern United States and analyzed by strong acid digestion. Foliage and bolewood was collected from 12 of the 26 sites and analyzed for total Mn and Ca. Our results show forest floor and mineral soil horizon Mn concentrations and Mn/Ca ratios were higher at Pennsylvania and New York sites than New Hampshire and Vermont sites. Using a modified isotope equation, enrichment factors (EF) for Mn/Ca ratios were calculated to be ~3.6 in the forest floor, upper and lower mineral soil horizons at sites in New York and Pennsylvania compared to reference sites in New Hampshire and Vermont. Foliar and bolewood Mn concentrations also decreased from Pennsylvania towards New Hampshire. Moreover, foliar and bolewood Mn concentrations were strongly correlated to forest floor, upper, and lower mineral soil Mn concentrations. It was hypothesized that internal cycling (uptake, throughfall, and litterfall) of Mn controls retention of enriched Mn in forests. Geologic influences from a lithologic gradient and soil pH gradient could also influence Mn enrichment in addition to Mn pollution. Ratios of Mn/Ca and other elemental ratios hold promise as geochemical tracers but require further development.

Teeth as a biomarker of past chemical exposure

PURPOSE OF REVIEW

Accurate prenatal exposure assessment is one of the major challenges in environmental epidemiologic studies. Variations in placental transport make maternal biospecimens unreliable for many chemicals and fetal specimens collected at birth do not provide information on exposure timing over the prenatal period.

RECENT FINDINGS

The skeletal compartment is an important chemical repository, making calcified tissues important for measuring exposure. For decades teeth have been used to estimate long-term cumulative exposure to metals and some organic chemicals. Recently developed methodologies that combine sophisticated histological and chemical analysis to precisely sample tooth layers that correspond to specific life stages have the potential to reconstruct exposure in the second and third trimesters of prenatal development and during early childhood.

SUMMARY

Such a retrospective biomarker that precisely measures exposure intensity and timing during prenatal development would substantially aid epidemiologic investigations, particularly case-control studies of rare health outcomes.

Strontium isotope evidence for landscape use by early hominins

Ranging and residence patterns among early hominins have been indirectly inferred from morphology, stone-tool sourcing, referential models and phylogenetic models. However, the highly uncertain nature of such reconstructions limits our understanding of early hominin ecology, biology, social structure and evolution. We investigated landscape use in Australopithecus africanus and Paranthropus robustus from the Sterkfontein and Swartkrans cave sites in South Africa using strontium isotope analysis, a method that can help to identify the geological substrate on which an animal lived during tooth mineralization. Here we show that a higher proportion of small hominins than large hominins had non-local strontium isotope compositions. Given the relatively high levels of sexual dimorphism in early hominins, the smaller teeth are likely to represent female individuals, thus indicating that females were more likely than males to disperse from their natal groups. This is similar to the dispersal pattern found in chimpanzees, bonobos and many human groups, but dissimilar from that of most gorillas and other primates. The small proportion of demonstrably non-local large hominin individuals could indicate that male australopiths had relatively small home ranges, or that they preferred dolomitic landscapes.

Does life consistently maximise energy intensity?

We propose that a basic biological imperative of all organisms is to maximise energy (E) intensity, defined as the average rate of energy use per unit area of the Earth's surface. The dominant organism in any given environment is predicted to be that exerting the greatest E intensity regardless of evolutionary origin. Our 'theory of biological E intensity' thus explains variation in life form in terms of adaptations as opposed to accidents of biological history. It defines the competitive criterion in all metabolic pathways and industrial processes as the average rate of kinetic energy use, excluding heating but including all directed biological kinesis at scales up to the whole organism. A suggested unit for E intensity is joules per square meter per year. Because catalysts are crucial to extremely rapid use of energy (and therefore maximisation of E intensity), catalytic nutrient elements can be viewed as the ultimate means of life. It follows that a common denominator of all dominant organisms would be the acquisition of an optimal catalytic formula as determined by concentrations and ratios of C, H, O, N, S, Na, Mg, P, K, Ca, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Se, Mo, Cd, I, W, and Hg. The likely local shortages of various of these elements can theoretically be alleviated by various changes in the size, shape, and/or behaviour of organisms, depending on the environment. Thus, the availability, and potential for supplementation, of catalytic elements would be the ultimate basis for adaptation, largely determining which life form dominates in any particular location. The theory predicts the following. (1) In nutrient-rich environments offering the optimal catalytic formula, dominant organisms will be microbes. This is because microbes, and prokaryotes in particular, excel in E intensity through rapid biomolecular turnover, enabling them to usurp resources despite minimising biomass, complexity, and information. (2) Where the environment is catabolically dystrophic (i.e. scarce in certain nutrients required for catabolism), macrobes (e.g. humans and trees) will be superior competitors because they can collect and supplement nutrients and thereby approach the optimal catalytic formula. This enables macrobes, despite having considerably slower metabolism per unit body mass, to enhance E intensity relative to competing microbes constrained by catabolic dystrophy. Finally, (3) where the environment is anabolically dystrophic (i.e. scarce in certain nutrients required for anabolism) microbes will again dominate because biomolecular turnover can be relatively free from constraint given the limited fuel available. We suggest that an important and overlooked way to achieve power is to reuse energy, and that all organisms maximise E intensity by converting chemical potential energy (i.e. in fuel) into circuits of electromagnetic energy comprising electric charge, photons, and excited electrons. Because space and time merge subatomically, these electromagnetic circuits represent a concentration in spacetime of energy that (1) is concurrently kinetic and static, hence available for immediate use yet also conserved with minimal dissipation, and (2) ultimately promotes catalysis, which we assert is the primary biological tactic for maximising E intensity and thus fitness.

Nutrient input–output budgets of tropical forest ecosystems: a review

Atmospheric gains and hydrologic losses of calcium, magnesium, potassium, phosphorus and nitrogen for 25 tropical forest sites on a variety of geological substrates are reviewed. The data set comprised 19 lowland and six montane sites. Twenty studies were subjected to further analysis after initial quality control. These were subdivided into forests on (1) very infertile soils (N = 5), (2) (moderately) infertile soils (N = 5), (3) moderately fertile soils (N = 4) and (4) fertile soils (N = 4). Two studies pertaining to large river basins were treated separately. Although variation in nutrient fluxes was large, reflecting both natural and methodological factors, scatter plots of annual calcium, magnesium and potassium losses v. annual runoff for small catchment areas revealed four groups with characteristic nutrient export patterns that corresponded closely with soil fertility levels. Element losses from the two large basins were much higher than those recorded for small basins in the same areas and were interpreted in terms of depths of weathering front, river incision and root network. Phosphorus accumulated in virtually all cases, reflecting the low mobility of the element. Nitrogen budgets were generally very incomplete. There is a need for more and careful studies of tropical forest nutrient budgets, especially for nitrogen. Standardization of methodology is essential if comparability of results is to be improved.

Nutrient content of bulk precipitation in south-central Java, Indonesia

The chemical composition of bulk precipitation was studied for a period totalling 18 months between 1975 and 1978 at a high rainfall site in central Java. The following elements were determined: calcium, magnesium, sodium, potassium, nitrate-nitrogen, chlorine, phosphate-phosphorus, silicon, aluminium, iron, manganese and pH. Ammoniacal nitrogen, total nitrogen and sulphate-sulphur were determined, during four weeks in May 1983. Concentrations of all elements rose dramatically during the exceptionally severe dry season of 1977 which may have caused accession rates for some nutrients to be overestimated (i.e. compared to a year with ‘normal’ rainfall) by about 10%. Results are explained in terms of prevailing wind directions and proximity to, or absence of, particular solute sources, such as the ocean, volcanoes or eroding lands.

Most elements exhibited intermediate concentrations when compared with data for other humid tropical locations; sodium and perhaps nitrogen were on the low side and pH on the high side of the spectrum. Annual accession rates at the study site were considerable by pan-tropical standards, mainly as a result of high rainfall totals. Comparing accession rates with 25-year-average nutrient immobilization rates in stemwood of local plantations ofPinus merkusiiJungh. et de Vr. andAgathis dammaraWarb. showed atmospheric inputs of magnesium and potassium to be high enough (theoretically) to account for losses of these elements in stemwood removal. Corresponding figures for nitrogen were 90% (Pinus) and 50% (Agathis), and for calcium and phosphorus 60 and 40% respectively (both species).

Strontium isotope ratios (87Sr/86Sr) of tooth enamel: a comparison of solution and laser ablation multicollector inductively coupled plasma mass spectrometry methods

Strontium isotope ratios (87Sr/86Sr) in tooth enamel provide a means to investigate migration and landscape use in humans and other animals. Established methods for measuring (87)Sr/(86)Sr in teeth use bulk sampling (5-20 mg) and labor-intensive elemental purification procedures before analysis by either thermal ionization mass spectrometry (TIMS) or multicollector inductively coupled plasma mass spectrometry (MC-ICP-MS). Another method for measuring 87Sr/86Sr is laser ablation MC-ICP-MS, but concerns have been expressed about its accuracy for measuring tooth enamel. In this study we test the precision and accuracy of the technique by analyzing 30 modern rodent teeth from the Sterkfontein Valley, South Africa by laser ablation MC-ICP-MS and solution MC-ICP-MS. The results show a mean difference in 87Sr/86Sr measured by laser ablation and by solution of 0.0003 +/- 0.0002. This degree of precision is well within the margin necessary for investigating the potential geographic origins of humans or animals in many areas of the world. Because laser ablation is faster, less expensive, and less destructive than bulk sampling solution methods, it opens the possibility for conducting 87Sr/86Sr analyses of intra-tooth samples and small and/or rare specimens such as micromammal and fossil teeth.

Sr and Pb isotopes as environmental indicators in environmental studies

An environmental indicator is a numerical or a descriptive categorization of environmental data with the primary purpose of assessing the affected environment. In these studies, two characteristic isotopes, namely Sr and Pb, were assessed of their ability to describe the affected environment in environmental studies by detecting trends of pollution over short as well as long time periods and by identifying sources of contamination. The ability of environmental indicators to serve as elements in summarizing the situation of the affected environment is discussed. An illustrative example is presented where lead isotopes are used to understand the source of pollution in Kozani, a small rural area in Greece. Conclusions are derived in terms of the source of the pollution in the specific area.