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1.
We tested the reliability of herbivore faecal δ 13C and δ 15N 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 δ 13C consistent with C 3 feeding, grazer faeces are C 4, and mixed-feeder faeces intermediate. Although the respective ranges do not overlap, there is significant variation in faecal δ 13C 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 δ 13C of C 3 and C 4 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 δ 13C 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 δ 15N tracks changes in plant δ 15N, 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 C 3/C 4 distinctions, although further understanding of variations in mammal δ 15N are needed for greater confidence in this approach. 相似文献
2.
Reviews in Fish Biology and Fisheries - Stable isotope analysis (SIA) is widely used to assess animal diet and movements, requiring accurate estimates of trophic discrimination factors (TDFs).... 相似文献
3.
Sea lion and seal populations in Alaskan waters underwent various degrees of decline during the latter half of the twentieth century and the cause(s) for the declines remain uncertain. The stable carbon ( 13C/ 12C) and nitrogen ( 15N/ 14N) isotope ratios in bone collagen from wild Steller sea lions ( Eumetopias jubatus), northern fur seals ( Callorhinus ursinus) and harbor seals ( Phoca vitulina) from the Bering Sea and Gulf of Alaska were measured for the period 1951-1997 to test the hypothesis that a change in trophic level may have occurred during this interval and contributed to the population declines. A significant change in ' 15N in pinniped tissues over time would imply a marked change in trophic level. No significant change in bone collagen ' 15N was found for any of the three species during the past 47 years in either the Bering Sea or the Gulf of Alaska. However, the 15N in the Steller sea lion collagen was significantly higher than both northern fur seals and harbor seals. A significant decline in ' 13C (almost 2 over the 47 years) was evident in Steller sea lions, while a declining trend, though not significant, was evident in harbor seals and northern fur seals. Changes in foraging location, in combination with a trophic shift, may offer one possible explanation. Nevertheless, a decrease in ' 13C over time with no accompanying change in ' 15N suggests an environmental change affecting the base of the foodweb rather than a trophic level change due to prey switching. A decline in the seasonal primary production in the region, possibly resulting from decreased phytoplankton growth rates, would exhibit itself as a decline in ' 13C. Declining production could be an indication of a reduced carrying capacity in the North Pacific Ocean. Sufficient quantities of optimal prey species may have fallen below threshold sustaining densities for these pinnipeds, particularly for yearlings and subadults who have not yet developed adequate foraging skills. 相似文献
4.
Although previous studies have shown that ecosystem functions are affected by either trophic structure or habitat structure, there has been little consideration of their combined effects. Such interactions may be particularly important in systems where habitat and trophic structure covary. I use the aquatic insects in bromeliads to examine the combined effects of trophic structure and habitat structure on a key ecosystem function: detrital processing. In Costa Rican bromeliads, trophic structure naturally covaries with both habitat complexity and habitat size, precluding any observational analysis of interactions between factors. I therefore designed mesocosms that allowed each factor to be manipulated separately. Increases in mesocosm complexity reduced predator (damselfly larva) efficiency, resulting in high detritivore abundances, indirectly increasing detrital processing rates. However, increased complexity also directly reduced the per capita foraging efficiency of the detritivores. Over short time periods, these trends effectively cancelled each other out in terms of detrital processing. Over longer time periods, more complex patterns emerged. Increases in mesocosm size also reduced both predator efficiency and detritivore efficiency, leading to no net effect on detrital processing. In many systems, ecosystem functions may be impacted by strong interactions between trophic structure and habitat structure, cautioning against examining either effect in isolation. 相似文献
5.
Stable isotopes ( δ15N and δ13C) are being widely applied in ecological research but there has been a call for ecologists to determine species- and tissue-specific diet discrimination factors (? 13C and ? 15N) for their study animals. For large sharks stable isotopes may provide an important tool to elucidate aspects of their ecological roles in marine systems, but laboratory based controlled feeding experiments are impractical. By utilizing commercial aquaria, we estimated ? 15N and ? 13C of muscle, liver, vertebral cartilage and a number of organs of three large sand tiger ( Carcharias taurus) and one large lemon shark ( Negaprion brevirostris) under a controlled feeding regime. For all sharks mean ± SD for ? 15N and ? 13C in lipid extracted muscle using lipid extracted prey data were 2.29‰ ± 0.22 and 0.90‰ ± 0.33, respectively. The use of non-lipid extracted muscle and prey resulted in very similar ? 15N and ? 13C values but mixing of lipid and non-lipid extracted data produced variable estimates. Values of ? 15N and ? 13C in lipid extracted liver and prey were 1.50‰ ± 0.54 and 0.22‰ ± 1.18, respectively. Non-lipid extracted diet discrimination factors in liver were highly influenced by lipid content and studies that examine stable isotopes in shark liver, and likely any high lipid tissue, should strive to remove lipid effects through standardising C:N ratios, prior to isotope analysis. Mean vertebral cartilage ? 15N and ? 13C values were 1.45‰ ± 0.61 and 3.75‰ ± 0.44, respectively. Organ ? 15N and ? 13C values were more variable among individual sharks but heart tissue was consistently enriched by ~ 1–2.5‰. Minimal variability in muscle and liver δ15N and δ13C sampled at different intervals along the length of individual sharks and between liver lobes suggests that stable isotope values are consistent within tissues of individual animals. To our knowledge, these are the first reported diet–tissue discrimination factors for large sharks under semi-controlled conditions, and are lower than those reported for teleost fish. 相似文献
6.
Stable isotope ratios (δ 15N and δ 13C) and diet of three fish species, Stegastes nigricans, Chaetodon citrinellus and Epinephelus merra, were analyzed on the fringing coral reefs of two bays that are differentially exposed to river runoff on Moorea Island, French Polynesia. S. nigricans and C. citrinellus relied mostly on turf algae and presented similar trophic levels and δ 15N values, whereas E. merra fed on large invertebrates (crabs and shrimps) and had higher trophic levels and δ 15N values. Discrepancies existed between stomach content and stable isotope analyses for the relative importance of food items. Bayesian mixing models indicated that sedimented organic matter was also an important additional food for S. nigricans and C. citrinellus, and fishes for E. merra. The main sources of organic matter involved in the food webs ending with these species were algal turfs and surface sediments, while water particulate organic matter was barely used. Significant spatial differences in C and N isotopic ratios for sources and fishes were found within and between bays. Lower 13C and higher 15N values were observed for various compartments of the studied trophic network at the end of each bay than at the entrance. Differences were observed between bays, with organic sources and consumers being, on average, slightly more 13C-depleted and 15N-enriched in Cook’s Bay than in Opunohu Bay, linked with a higher mean annual flow of the river at Cook’s Bay. Our results suggest that rivers bring continental material into these two bays, which is partly incorporated into the food webs of fringing coral reefs at least close to river mouths. Thus, continental inputs can influence the transfer of organic matter within coral reef food webs depending on the diet of organisms. 相似文献
7.
We evaluated the effects of ecosystem composition and structure (species richness and diversity, cover and spatial attributes of vegetation), abiotic factors (climate and topographical features) and the condition of the bare-ground areas (evaluated using soil-surface indicators) on the performance of Stipa tenacissima [evaluated using foliar 13C, 15N, nitrogen concentration and the carbon-to-nitrogen (C:N) ratio] in 15 steppes of SE Spain. Foliar 13C values of S. tenacissima showed a low degree of variation in the studied steppes, with average values ranging from –24.1 to –22.9. Higher variation was found in the 15N values, which ranged from –5.5 to –2.4. The nitrogen concentration and the C:N ratio varied between 5.0 and 8.0 mg g –1, and between 55.4 and 85.3, respectively. The 13C values became less negative with increasing spatial aggregation of perennial vegetation, while the C:N values increased with increasing perennial vegetation cover. The 15N values became more negative with increasing infiltration in the bare-ground areas, but the nitrogen concentration was not related to any of the environmental variables measured. Our results suggest that the relative importance of ecosystem structure and soil-surface conditions in the bare ground areas was higher than that of abiotic factors as determinants of the performance of S. tenacissima. The results also show that even subtle changes in these ecosystem features may lead to modifications in plant performance in semiarid S. tenacissima steppes, and thus to modifications in the associated ecosystem functions in the mid- to long-term. 相似文献
8.
Hydrobiologia - Fishers’ ecological knowledge (FEK) has contributed to a better understanding about the reproduction of fishery resources, especially where biological data are scarce or... 相似文献
9.
The food-web structure of the Arctic deep Canada Basin was investigated in summer 2002 using carbon and nitrogen stable isotope tracers. Overall food-web length of the range of organisms sampled occupied four trophic levels, based on 3.8 trophic level enrichment ( 15N range: 5.3–17.7). It was, thus, 0.5–1 trophic levels longer than food webs in both Arctic shelf and temperate deep-sea systems. The food sources, pelagic particulate organic matter (POM) ( 13C=–25.8, 15N=5.3) and ice POM ( 13C=–26.9, 15N=4.1), were not significantly different. Organisms of all habitats, ice-associated, pelagic and benthic, covered a large range of 15N values. In general, ice-associated crustaceans ( 15N range 4.6–12.4, mean 6.9) and pelagic species ( 15N range 5.9–16.5, mean 11.5) were depleted relative to benthic invertebrates ( 15N range 4.6–17.7, mean 13.2). The predominantly herbivorous and predatory sympagic and pelagic species constitute a shorter food chain that is based on fresh material produced in the water column. Many benthic invertebrates were deposit feeders, relying on largely refractory material. However, sufficient fresh phytodetritus appeared to arrive at the seafloor to support some benthic suspension and surface deposit feeders on a low trophic level (e.g., crinoids, cumaceans). The enriched signatures of benthic deposit feeders and predators may be a consequence of low primary production in the high Arctic and the subsequent high degree of reworking of organic material. 相似文献
10.
Functional aspects of biodiversity were investigated in a lowland tropical rainforest in French Guyana (5°2′N, annual precipitation
2200 mm). We assessed leaf δ 15N as a presumptive indicator of symbiotic N 2 fixation, and leaf and wood cellulose δ 13C as an indicator of leaf intrinsic water-use efficiency (CO 2 assimilation rate/leaf conductance for water vapour) in dominant trees of 21 species selected for their representativeness
in the forest cover, their ecological strategy (pioneers or late successional stage species, shade tolerance) or their potential
ability for N 2 fixation. Similar measurements were made in trees of native species growing in a nearby plantation after severe perturbation
(clear cutting, mechanical soil disturbance). Bulk soil δ 15N was spatially quite uniform in the forest (range 3–5‰), whereas average leaf δ 15N ranged from −0.3‰ to 3.5‰ in the different species. Three species only, Diplotropis purpurea, Recordoxylon speciosum (Fabaceae), and Sclerolobium melinonii (Caesalpiniaceae), had root bacterial nodules, which was also associated with leaf N concentrations higher than 20 mg g −1. Although nodulated trees displayed significantly lower leaf δ 15N values than non-nodulated trees, leaf δ 15N did not prove a straightforward indicator of symbiotic fixation, since there was a clear overlap of δ 15N values for nodulated and non-nodulated species at the lower end of the δ 15N range. Perturbation did not markedly affect the difference δ 15N soil − δ 15N leaf, and thus the isotopic data provide no evidence of an alteration in the different N acquisition patterns. Extremely large
interspecific differences in sunlit leaf δ 13C were observed in the forest (average values from −31.4 to −26.7‰), corresponding to intrinsic water-use efficiencies (ratio
CO 2 assimilation rate/leaf conductance for water vapour) varying over a threefold range. Wood cellulose δ 13C was positively related to total leaf δ 13C, the former values being 2–3‰ higher than the latter ones. Leaf δ 13C was not related to leaf δ 15N at either intraspecific or interspecific levels. δ 13C of sunlit leaves was highest in shade hemitolerant emergent species and was lower in heliophilic, but also in shade-tolerant
species. For a given species, leaf δ 13C did not differ between the pristine forest and the disturbed plantation conditions. Our results are not in accord with the
concept of existence of functional types of species characterized by common suites of traits underlying niche differentiation;
rather, they support the hypothesis that each trait leads to a separate grouping of species.
Received: 18 August 1997 / Accepted: 14 April 1998 相似文献
11.
Background and AimsPhosphorus (P) mineralisation from crop residues is usually predicted from total P or carbon: phosphorus (C: P) ratios. However, these measures have limited accuracy as they do not take into account the presence of different P species that may be mineralised at different rates. In this study P speciation was determined using solution 31P nuclear magnetic resonance (NMR) spectroscopy to understand the potential fate of residue P in soils. MethodsMature above-ground biomass of eight different crops sampled from the field was portioned into stem, chaff and seed. ResultsThe main forms of P detected in stem and chaff were orthophosphate (25–75 %), phospholipids (10–40 %) and RNA (5–30 %). Phytate was the dominant P species in seeds, and constituted up to 45 % of total P in chaff but was only detected in minor amounts (<1 %) in stem residue. The majority (65–95 %) of P in stems was water-extractable, and most of this was detected as orthophosphate. However, this includes organic P that may have been hydrolysed during the water extraction. ConclusionsThis study indicates that the majority of residue P in aboveground plant residues has the potential to be delivered to soil in a form readily available to plants and soil microorganisms. 相似文献
12.
The effects of anticoagulant EDTA and sodium heparin (SH) on stable carbon δ 13C and nitrogen δ 15N isotopic values of red blood cells (RBC) and blood plasma in juvenile blacktip reef sharks Carcharhinus melanopterus were analysed. Plasma preserved with anticoagulants was not isotopically distinct from plasma stored in no-additive control tubes but RBC δ 15N values exhibited small enrichments when preserved with EDTA and SH. Results suggest EDTA and SH are viable anticoagulants for stable isotopic analyses of blood fractions but further studies are advised to validate results. 相似文献
13.
Regional food web studies that fail to account for small-scale isotopic variability can lead to a mismatch between an organism’s
inferred and true trophic position. Misinterpretation of trophic status may result, substantially limiting spatial and temporal
comparability of food web studies. We sampled several carbon sources and consumers in a nested design to assess the variability
of food web members across small spatial scales (100 s of m to several km) in regions around the Windmill Islands and Vestfold
Hills in East Antarctica. For carbon sources, δ 13C in sea ice POM was particularly variable between locations (km apart) and between sites (100 s of m apart) with replicate
samples varying by up to 16‰. Macroalgae δ 13C was less variable (replicate samples ranging up to 6.9‰ for the red alga Iridaea cordata), yet still differed between locations. Sediment POM and pelagic POM were the least variable, displaying minimal differences
between locations or sites for δ 13C and δ 15N. Three out of eight consumers were significantly different between locations for δ 13C, and five out of eight for δ 15N, with the fish Trematomus bernacchii the most variable for both δ 13C and δ 15N. At smaller scales, the amphipod Paramorea walkeri showed significant variation between sites in δ 13C but not in δ 15N. We attribute small-scale variability to the dynamic physical environment for carbon sources in coastal systems and a close
coupling of diet to habitat for consumers. We highlight the need to account for small-scale spatial variation in sampling
designs for regional food web studies. 相似文献
14.
Recent studies have shown that the tussock grass Stipa tenacissima L. facilitates the establishment of late-successional shrubs, in what constitutes the first documented case of facilitation of woody plants by grasses. With the aim of increasing our knowledge of this interaction, in the present study we investigated the effects of S. tenacissima on the foliar δ13C, δ15N, nitrogen concentration, and carbon: nitrogen ratio of introduced seedlings of Pistacia lentiscus L., Quercus coccifera L., and Medicago arborea L. in a semi-arid Mediterranean steppe. Six months after planting, the values of δ13C ranged between -26.9‰ and -29.6‰,whereas those of δ15N ranged between -1.9‰ and 2.7‰. The foliar C: N ratio ranged between 10.7 and 53.5,and the nitrogen concentration ranged between 1.0% and 4.4%. We found no significant effect of the microsite provided by S. tenacissima on these variables in any of the species evaluated. The values of δ13C were negatively correlated with predawn water potentials in M. arborea and were positively correlated with relative growth rate in Q. coccifera. The values of δ15N were positively correlated with the biomass allocation to roots in the latter species. The present results suggest that the modification of environmental conditions in the are surrounding S. tenacissima was not strong enough to modify the foliar isotopic and nitrogen concentration of shrubs during the early stages after planting. 相似文献
16.
Stable nitrogen (δ 15N) and carbon (δ 13C) isotope ratios from muscle, liver and yolk were analysed from the mother and embryos of an ovoviviparous shark, Hexanchus griseus. Embryonic liver and muscle had similar δ 15N and δ 13C ratios or were depleted in heavy isotopes, compared to the same maternal somatic and reproductive yolk tissues, but no relationship existed between δ 15N or δ 13C and embryo length, as expected, because a switch to placental nourishment is lacking in this species. This study expands the understanding of maternal nourishment and embryonic stable isotope differences in ovoviviparous sharks. 相似文献
17.
Abstract Leiopelma hochstetteri, the most widespread of New Zealand's native frogs, is recognised as threatened, and is fully protected by legislation. As a first step to characterise the diet and trophic level of L. hochstetteri within streams in the Waitakere Ranges, Auckland, stable carbon and nitrogen isotope analyses were undertaken on a variety of sympatric terrestrial and aquatic plant and animal species, including adult frogs. These results show that: (1) aquatic and terrestrial food webs are linked by terrestrial inputs into the stream; (2) invertebrate and vertebrate predators separate well into distinct trophic groups, and (3) L. hochstetteri occupies an intermediate trophic position among predators, with a diet, at least as an adult, comprising terrestrial invertebrates. Shortfin eels and banded kokopu are identified as potential predators of L. hochstetteri, but data for rats are inconclusive. These results have important implications for the conservation of New Zealand native frog species and riparian stream habitat. 相似文献
18.
Wing membranes of laboratory and field-reared monarch butterflies ( Danaus plexippus) were analyzed for their stable-hydrogen (δD) and carbon (δ 13C) isotope ratios to determine whether this technique could be used to identify their natal origins. We hypothesized that
the hydrogen isotopic composition of monarch butterfly wing keratin would reflect the hydrogen isotope patterns of rainfall
in areas of natal origin where wings were formed. Monarchs were reared in the laboratory on milkweed plants ( Asclepias sp.) grown with water of known deuterium content, and, with the assistance of volunteers, on native milkweeds throughout
eastern North America. The results show that the stable hydrogen isotopic composition of monarch butterflies is highly correlated
with the isotopic composition of the milkweed host plants, which in turn corresponds closely with the long-term geographic
patterns of deuterium in rainfall. Stable-carbon isotope values in milkweed host plants were similarly correlated with those
values in monarch butterflies and showed a general pattern of enrichment along a southwest to northeast gradient bisecting
the Great Lakes. These findings indicate that natal origins of migratory and wintering monarchs in Mexico can be inferred
from the combined δD and δ 13C isotopic signatures in their wings. This relationship establishes that analysis of hydrogen and carbon isotopes can be used
to answer questions concerning the biology of migratory monarch butterflies and provides a new approach to tracking similar
migratory movements of other organisms.
Received: 1 July 1998 / Accepted: 11 November 1998 相似文献
19.
Much of the primatology literature on stable isotope ratios of carbon (δ 13C) and nitrogen (δ 15N) has focused on African and New World species, with comparatively little research published on Asian primates. Here we present hair δ 13C and δ 15N isotope values for a sample of 33 long-tailed macaques from Singapore. We evaluate the suggestion by a previous researcher that forest degradation and biodiversity loss in Singapore have led to a decline in macaque trophic level. The results of our analysis indicated significant spatial variability in δ 13C but not δ 15N. The range of variation in δ 13C was consistent with a diet based on C 3 resources, with one group exhibiting low values consistent with a closed canopy environment. Relative to other macaque species from Europe and Asia, the macaques from Singapore exhibited a low mean δ 13C value but mid-range mean δ 15N value. Previous research suggesting a decline in macaque trophic level is not supported by the results of our study. 相似文献
20.
Plant and Soil - Agricultural soils in Germany store 2.54 Pg of organic carbon (C). However, information about how and when this C entered the soils is limited. This study illustrates how depth... 相似文献
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