Tracking Cats: Problems with Placing Feline Carnivores on ��18O, ��D Isoscapes

Background

Several felids are endangered and threatened by the illegal wildlife trade. Establishing geographic origin of tissues of endangered species is thus crucial for wildlife crime investigations and effective conservation strategies. As shown in other species, stable isotope analysis of hydrogen and oxygen in hair (δD_h, δ¹⁸O_h) can be used as a tool for provenance determination. However, reliably predicting the spatial distribution of δD_h and δ¹⁸O_h requires confirmation from animal tissues of known origin and a detailed understanding of the isotopic routing of dietary nutrients into felid hair.

Methodology/Findings

We used coupled δD_h and δ¹⁸O_h measurements from the North American bobcat (Lynx rufus) and puma (Puma concolor) with precipitation-based assignment isoscapes to test the feasibility of isotopic geo-location of felidae. Hairs of felid and rabbit museum specimens from 75 sites across the United States and Canada were analyzed. Bobcat and puma lacked a significant correlation between H/O isotopes in hair and local waters, and also exhibited an isotopic decoupling of δ¹⁸O_h and δD_h. Conversely, strong δD and δ¹⁸O coupling was found for key prey, eastern cottontail rabbit (Sylvilagus floridanus; hair) and white-tailed deer (Odocoileus virginianus; collagen, bone phosphate).

Conclusions/Significance

Puma and bobcat hairs do not adhere to expected pattern of H and O isotopic variation predicted by precipitation isoscapes for North America. Thus, using bulk hair, felids cannot be placed on δ¹⁸O and δD isoscapes for use in forensic investigations. The effective application of isotopes to trace the provenance of feline carnivores is likely compromised by major controls of their diet, physiology and metabolism on hair δ¹⁸O and δD related to body water budgets. Controlled feeding experiments, combined with single amino acid isotope analysis of diets and hair, are needed to reveal mechanisms and physiological traits explaining why felid hair does not follow isotopic patterns demonstrated in many other taxa.     

The environmental water of the middle Eocene Arctic: Evidence from δD, δ18O and δ13C within specific compounds

The extensive vertical exposure (> 150 m) of terrestrial sediments on Axel Heiberg Island, which contain thick fossiliferous lignites, presents an exceptional opportunity to follow the establishment and re-establishment of Arctic Metasequoia forests during the middle Eocene. We compared δD values in n-alkanes of chain length 23, 25, 27 and 29 with δ¹⁸O values in phenylglucosazone (P-G) derived from α-cellulose; we also analyzed %-abundance of ferns, gymnosperms and angiosperms using pollen and spores isolated from each lignite. Our results showed that forest composition was altered upon uplift, as gymnosperms became more abundant within the relatively well-drained upland sediments. This was also reflected in the small (1‰), but significant, increase in the δ¹³C value of TOM from lowland to upland environments. However, neither the δD values of n-alkanes nor the δ¹⁸O in P-G were statistically different in the upland sediments, as compared to the lowland sediments; from this we inferred that the oxygen isotope signature of environmental water available to the forests for plant growth was relatively uniform throughout the time of the fossil forests. The δD value of environmental water implied by both n-alkanes and P-G ranged from ? 168 to ? 131% and was considerably enriched compared to all environmental water samples available from the modern Arctic region (< ? 180%). In addition to indicating a warmer Eocene Arctic, subject to meteoric transport patterns different from today's, these results argue against the presence of an Eocene polar ice cap.     

Water use by woody plants on contrasting soils in a savanna parkland: assessment with δ2H and δ18O

In savanna parklands of southern Texas, patches of grassland and discrete clusters of small trees and shrubs occur on sandy loam surface soils underlain by an argillic horizon (claypan) at 40 cm. Large trees and shrubs in groves occur on deep (2 m) sandy loam soils without an argillic horizon. 2H and 18O of rainfall, groundwater, and soil and plant water were measured to: (1) determine if coexistence in woody patches occurs via vertical stratification of soil water uptake; (2) document differences in plant water acquisition on contrasting soil types; and (3) evaluate recharge and evaporative losses of soil moisture from grassland vs. wooded landscape elements. Groundwater was isotopically similar to weighted rainfall, suggesting local recharge at this site. Linear regressions of soil water 2H on 18O yielded slopes less than the meteoric water line, indicating significant evaporative losses of soil moisture in all landscape elements. Interspecific differences in root density distribution were significant; some woody species had roots well below 1.6 m, while others had few roots below 0.8 m. 2H and 18O values of stem water from all plants in groves were lower than those of soil water in the upper 1.5 m of the profile, suggesting all species obtained their water from depths >1.5 m. Deep roots of trees and shrubs at this savanna parkland site thus appeared to have a functional significance that was not revealed by biomass or density determinations. Root densities of species in discrete clusters (claypan present) were typically greater than those of the same species in groves (claypan absent), especially in the upper 80 cm of the soil profile. Consistent with rooting profiles, 2H and 18O values of plant water indicated that trees and shrubs in discrete clusters with fine- textured subsoils obtained most of their water at depths <1.5 m. As with groves, there was no indication of water resource partitioning between species. In summary, we saw no isotopic evidence that co- occurring woody plants at this savanna parkland site were partitioning soil moisture vertically during late summer/early fall, despite marked differences in their root density distributions. This supports other lines of evidence which indicate that species interactions in tree/shrub clumps are competitive, and that species composition is therefore unstable in those landscape elements.     

Tree age,site and climate controls on tree ring cellulose δ18O: A case study on oak trees from south-western France

A main concern of dendroclimatic reconstruction is to distinguish in the tree ring proxy the influence of the climate variables of interest from other controlling factors. In order to investigate age, site and climate controls on tree ring width and cellulose δ¹⁸O, measurements have been performed in nearby groups of young (145 years old) and older (310–405 years old) oak trees in south-western France, covering the period 1860–2010.Within a given site, inter-tree deviations are small, pointing to a common climatic signal. Despite a similar inter-annual variability, the average level of cellulose δ¹⁸O in the young tree group is ∼0.8‰ higher than in the old trees. Such offsets might be caused by different soil properties and differences in the fraction of the source water used by trees from different depths. The δ¹⁸O of water in the top soil layer is directly related to the current growing season precipitation, while deeper water can have a lower and more constant δ¹⁸O. Local cave drip waters at 10 m depth indeed show a constant isotopic composition, which corresponds to pluri-annual mean precipitation.A 2‰ increasing trend is observed in cellulose δ¹⁸O of young trees in the first 30 years of growth, during a period when no trend is visible in older trees. This increase can be quantitatively explained by humidity gradients under the forest canopy, and a changing microclimate around the crown as trees grow higher.While relationships between tree ring width and climate appear complex, the isotopic composition of cellulose is strongly correlated with summer maximum temperature, relative humidity and evapotranspiration (r ≈ 0.70). Weaker correlations (r ≈ 0.40) are identified with precipitation δ¹⁸O from a 15-year long local record and from the REMOiso model output. These results imply that leaf water enrichment has a stronger control on the inter-annual variability of cellulose δ¹⁸O than the δ¹⁸O of precipitation.This study demonstrates the suitability of oak tree ring cellulose δ¹⁸O for reconstructing past summer climate variability in south-western France, provided that the sampling and pooling strategy accounts for the fact that trees from different sites and of different age can introduce non-climatic signals.     

The application of δ¹⁸O and δD for understanding water pools and fluxes in a Typha marsh

The δ¹⁸O and δD composition of water pools (leaf, root, standing water and soil water) and fluxes [transpiration (T), evaporation (E)] were used to understand ecohydrological processes in a managed Typha latifolia L. freshwater marsh. We observed isotopic steady‐state T and deep rooting in Typha. The isotopic mass balance of marsh standing water showed that E accounted for 3% of the total water loss, T accounted for 17% and subsurface drainage (D) accounted for the majority (80%). There was a vertical gradient in water vapour content and isotopic composition within and above the canopy sufficient for constructing an isotopic mass balance of water vapour during some sampling periods. During these periods, the proportion of T in evapotranspiration (T/ET) was between 56 ± 17% and 96 ± 67%, and the estimated error was relatively high (>37%) because of non‐local, background sources in vapour. Independent estimates of T/ET using eddy covariance measurements yielded similar mean values during the Typha growing season. The various T/ET estimates agreed that T was the dominant source of marsh vapour loss in the growing season. The isotopic mass balance of water vapour yielded reasonable results, but the mass balance of standing water provided more definitive estimates of water losses.     

Technical note: some observations on the conversion of dental enamel δ18O(p) values to δ18O(w) to determine human mobility

It has become a widespread practice to convert δ(18)O(p) values measured in human and animal dental enamel to a corresponding value of δ(18)O(w) and compare these data with mapped δ(18)O(w) groundwater or meteoric water values to locate the region where the owner of the tooth lived during the formation of the enamel. Because this is a regression procedure, the errors associated with the predicted δ(18)O(w) values will depend critically on the correlation between the comparative data used to perform the regression. By comparing four widely used regression equations we demonstrate that the smallest 95% error is likely to be greater than ±1% in δ(18)O(w) , and could be as large as ±3.5%. These values are significantly higher than those quoted in some of the recent literature, and measurements with errors at the higher end of this range would render many of the published geographical attributions statistically unsupportable. We suggest that the simplest solution to this situation is to make geographical attributions based on the direct comparison of measured values of δ(18)O(p) rather than on predicted values of δ(18)O(w).     

Structure of ferrichrome-type siderophores with dissimilarN δ-acyl groups: Asperchrome B1,B2,3,D1, D2 and D3

Summary Asperchromes are a series of iron-chelating compounds which contain a cyclic hexapeptide backbone as in ferrichrome siderophores and differ from the latter in having heterogenous acyl groups in the ornithine side chains. The molecular structures of the asperchrome B and D series have been determined by¹H- and¹³C-NMR spectroscopy; single-crystal X-ray diffraction was used to determine the detailed structural features of asperchrome B₁ and asperchrome D₁. Asperchrome B₁ crystallizes in the triclinic space group P1 witha= 1.3143(5) nm,b=1.2200(5) nm,c=0.8949(3) nm,=105.17(4)°,=94.03(3)°, =109.65(3)°,V=1.2843 nm³,Z=1, _x =1.446 g cm^–3. FinalR=0.054 for 4625 reflections measured at 138 K using MoK. Asperchrome D₁ crystallizes in the monoclinic space group P2₁ witha=1.2248(11) nm,b=1.3795(9) nm,c=1.3644(6) nm,=93.24(6)°,V=2.3016 nm³,Z=2, _x =1.418 g cm^–3. FinalR=0.110 for 3180 reflections measured at 138 K using MoK radiation. The conformation of the molecular backbone and iron coordination geometry in both asperchrome B₁ and D₁ compare well with those observed in other known ferrichrome siderophores. The differences in the acyl groups are illustrated and the structural results are correlated with their iron transport properties.     

[Zn(phen)(O,N,O)(H2O)] and [Zn(phen)(O,N)(H2O)] with O,N,O?is?2,6-dipicolinate and N,O?is?l-threoninate: synthesis, characterization, and biomedical properties

Two ternary Zn(II) complexes, with 1,10-phenanthroline (phen) as the main ligand and a carboxylate-containing ligand [dipicolinate (dipico) or L-threoninate (L-Thr)] as the subsidiary ligand, were prepared and characterized by elemental analysis, Fourier transform IR, UV, and fluorescence spectroscopy, X-ray diffraction, molar conductivity, and electrospray ionization mass spectrometry. X-ray structure analysis shows that both [Zn(phen)(dipico)(H(2)O)]·H(2)O (1) and [Zn(phen)(L-Thr)(H(2)O)Cl]·2H(2)O (2) have octahedral geometry about the Zn(II) atom. Both complexes can inhibit topoisomerase I, and have better anticancer activity than cisplatin against nasopharyngeal cancer cell lines, HK1 and HONE-1, with concentrations causing 50?% inhibition of cell proliferation (IC(50)) in the low micromolar range. Complex 2 has the highest therapeutic index for HK1. Both Zn(II) complexes can induce cell death by apoptosis. Changing the subsidiary ligand in the Zn(II) complexes affects the UV-fluorescence spectral properties of the coordinated phen ligand, the binding affinity for some DNA sequences, nucleobase sequence-selective binding, the phase at which cell cycle progression was arrested for treated cancer cells, and their therapeutic index.     

Listening In on the Past: What Can Otolith δ18O Values Really Tell Us about the Environmental History of Fishes?

Oxygen isotope ratios from fish otoliths are used to discriminate marine stocks and reconstruct past climate, assuming that variations in otolith δ¹⁸O values closely reflect differences in temperature history of fish when accounting for salinity induced variability in water δ¹⁸O. To investigate this, we exploited the environmental and migratory data gathered from a decade using archival tags to study the behaviour of adult plaice (Pleuronectes platessa L.) in the North Sea. Based on the tag-derived monthly distributions of the fish and corresponding temperature and salinity estimates modelled across three consecutive years, we first predicted annual otolith δ¹⁸O values for three geographically discrete offshore sub-stocks, using three alternative plausible scenarios for otolith growth. Comparison of predicted vs. measured annual δ¹⁸O values demonstrated >96% correct prediction of sub-stock membership, irrespective of the otolith growth scenario. Pronounced inter-stock differences in δ¹⁸O values, notably in summer, provide a robust marker for reconstructing broad-scale plaice distribution in the North Sea. However, although largely congruent, measured and predicted annual δ¹⁸O values of did not fully match. Small, but consistent, offsets were also observed between individual high-resolution otolith δ¹⁸O values measured during tag recording time and corresponding δ¹⁸O predictions using concomitant tag-recorded temperatures and location-specific salinity estimates. The nature of the shifts differed among sub-stocks, suggesting specific vital effects linked to variation in physiological response to temperature. Therefore, although otolith δ¹⁸O in free-ranging fish largely reflects environmental temperature and salinity, we counsel prudence when interpreting otolith δ¹⁸O data for stock discrimination or temperature reconstruction until the mechanisms underpinning otolith δ¹⁸O signature acquisition, and associated variation, are clarified.     

Influence of gabaculine on growth,chlorophyll synthesis,and δ-aminolevulinic acid synthase activity in Euglena gracilis

Euglena gracilis is capable of forming the heme and chlorophyll precursor δ-aminolevulinic acid (ALA) by two routes: from glutamate via the five-carbon path in the chloroplasts, and by ALA synthase-mediated condensation of succinyl-CoA and glycine, probably in the mitochondrion. 5-Amino-1,3-cyclohexadienyl carboxylic acid (gabaculine), a powerful inhibitor of ALA formation via the five-carbon path, was administered to E. gracilis Klebs strain Z Pringsheim cells growing in the light or dark, and its effects on growth, chlorophyll accumulation and extractable ALA synthase activity were measured. Gabaculine had no effect in vitro on ALA synthase or ALA dehydratase, even at 100 μM. Administration of 100 μM gabaculine to wild-type cells growing in the light slowed growth, inhibited chlorophyll accumulation, and induced an increase in extractable ALA synthase activity. Chlorophyll accumulation in the light was abolished by prior administration of the compound to growing cells for 6 h in the dark, whereas chlorophyll accumulation in cells without gabaculine began immediately after transfer to light. Extractable ALA synthase activity from gabaculine-pretreated dark-grown cells was initially lower than the activity from untreated cells, but it did not undergo a further decline after transfer of the cells to the light, whereas the activity from untreated cells dropped to less than one eighth the dark level after 2 h in the light, and by 4 h had fallen to a level five times lower than that extractable from gabaculine-treated cells. These results suggest that suppression of ALA synthase activity by light in untreated cells is related to light-induced activation of the five-carbon ALA biosynthetic pathway in the plastids, and may result from a contribution by a product of the five-carbon pathway to non-plastid tetrapyrrole pools in the light.     

Climatic adaptability of populations ofDiplotaxis erucoides D.C. (Brassicaceae) from Sicily,based on leaf morphology,leaf anatomy and δ13 C studies

The morphological and anatomical variability ofDiplotaxis erucoides populations from Sicily was investigated. Populations growing during the summer months exhibit distinct xeromorphic features. Leaf area is strongly reduced and leaf thickness is increased when compared with winter populations. Cell size, as well as cell arrangement and mesophyll cell surface area differ significantly between summer and winter populations. Leaf thickness is almost three times higher in summer populations andA (cell)/A, i.e. the mesophyll cell surface area per unit leaf area changes from about 16 for winter populations to almost 52 for summer populations. These differences are partly due to differences in intercellular volume and partly due to alterations in mesophyll cell sizes. The organic materal of the summer populations exhibits ¹³C values in the order of –27%. to –28%., while the corresponding values for the winter populations are in the order of –31%. to –33%.. Analysis ofD. erucoides populations from the transition period revealed intermediate ¹³C values. Anatomical variations such as reductions or increases ofA (cells)/A and changes of intercellular volume correlate with the corresponding ¹³C data. The ¹³C data are discussed in conjunction with the differences in leaf anatomy.