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1.
Application of stable isotope data to trophic studies requires understanding of factors influencing the isotopic discrimination factor (Δ) between consumers and their prey resources. This is missing for many omnivorous species, despite their diet and environment potentially impacting Δ. The effects of temperature, diet (including formulated feeds) and tissue type on Δ13C and Δ15N were thus tested experimentally. A temperature experiment exposed three species to identical diets at 18 and 23°C, whereas a diet experiment exposed one species to four diets at 18°C. At 23°C, C:N ratios, Δ13C and Δ15N were generally elevated versus 18°C. After lipid correction, tissue/species-specific differences at 23°C in Δ13C and Δ15N were up to 0.73 and 0.54‰ higher, respectively. Across the four diets, there were also significant differences in Δ13C and Δ15N between a natural diet and diets based on formulated feeds. Δ13C and Δ15N of muscle were 1.51 to 2.76‰ and 3.13 to 5.44‰, respectively. Highest Δ for both isotopes was from a formulated feed based on plant material that resulted in lower dietary protein content and quality. Thus, diet and environment fundamentally affected the isotopic discrimination factors and these factors require consideration within trophic studies based on stable isotopes. 相似文献
2.
The farming of shrimp is developing quickly worldwide, and recently, ingredients such as seaweeds in low proportion (25 to 4 %), incorporated into the commercial food, have been shown to improve the shrimp productive variables. The change of commercial foods to commercial feed with a proportion of natural food, and finally, to natural food has been little and simultaneously evaluated. The aim of our study was to determine the relative contribution of dietary carbon to the growth of Litopenaeus vannamei fed with a proportion of 4 % Sargassum (δ13C = ?20.9?±?0.05?‰), 4 % Ulva (δ13C = ?20.6?±?0.6?‰) meal, and a control diet (δ13C?=??22.6?±?0.2?‰) in 60-L tanks for 30 days, and finally, with the green seaweed Ulva spp. (δ13C = ?13.2?±?0.25?‰) and Ulva meal (δ13C = ?14.5?±?0.6?‰) in open-air ponds for 120 days, by measuring δ13C for each of the foods and in the muscle of shrimp. After 15 days, the rates of metabolic turnover (Δ13C = δ13Cshrimp ? δ13Cfood) were constant until the end of the experiment in the tanks. The muscle of shrimp assimilated carbon from all diets, which demonstrated the potential use of combined diets and the optimization of their use in diets containing seaweed. Our data will be useful in future interpretations of field and laboratory isotopic values for this species. 相似文献
3.
P.A. Barriga J.V. Sloan S.D. Porter C.L. Sagers 《Entomologia Experimentalis et Applicata》2013,149(3):265-272
Ecologists use stable isotopes to infer diets and trophic levels of animals in food webs, yet some assumptions underlying these inferences have not been thoroughly tested. We used laboratory‐reared colonies of Solenopsis invicta Buren (Hymenoptera: Formicidae: Solenopsidini) to test the effects of metamorphosis, diet, and lipid storage on carbon and nitrogen stable isotope ratios. Effects of metamorphosis were examined in ant colonies maintained on a control diet of domestic crickets and sucrose solution. Effects of a diet shift were evaluated by adding a tuna supplement to select colonies. Effects of lipid content on stable isotopes were tested by treating worker ants with polar and non‐polar solvents. δ13C and δ15N values of larvae, pupae, and workers were measured by mass spectrometry on whole‐animal preparations. We found a significant effect of colony age on δ13C, but not δ15N; larvae, pupae, and workers collected at 75 days were slightly depleted in 13C relative to collections at 15 days (Δδ13C = ?0.27‰). Metamorphosis had a significant effect on δ15N, but not δ13C; tissues of each successive developmental stage were increasingly enriched in 15N (pupae, +0.5‰; workers, +1.4‰). Availability of tuna resulted in further shifts of about +0.6‰ in isotope ratios for all developmental stages. Removing fat with organic solvents had no effect on δ13C, but treatment with a non‐polar solvent resulted in enriched δ15N values of +0.37‰. Identifying regular patterns of isotopic enrichment as described here should improve the utility of stable isotopes in diet studies of insects. Our study suggests that researchers using 15N enrichment to assess trophic levels of an organism at different sites need to take care not to standardize with immature insect herbivores or predators at one site and mature ones at another. Similar problems may also exist when standardizing with holometabolous insects at one site and spiders or hemimetabolous insects at another site. 相似文献
4.
Nigel E. Hussey Jaclyn Brush Ian D. McCarthy Aaron T. Fisk 《Comparative biochemistry and physiology. Part A, Molecular & integrative physiology》2010,155(4):445-453
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
5.
Diet quality influences isotopic discrimination among amino acids in an aquatic vertebrate
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Yoshito Chikaraishi Shawn A. Steffan Yoshinori Takano Naohiko Ohkouchi 《Ecology and evolution》2015,5(10):2048-2059
Stable nitrogen isotopic composition of amino acids (δ15NAA) has recently been employed as a powerful tool in ecological food web studies, particularly for estimating the trophic position (TP) of animal species in food webs. However, the validity of these estimates depends on the consistency of the trophic discrimination factor (TDF; = Δδ15NAA at each shift of trophic level) among a suite of amino acids within the tissues of consumer species. In this study, we determined the TDF values of amino acids in tadpoles (the Japanese toad, Bufo japonicus) reared exclusively on one of three diets that differed in nutritional quality. The diets were commercial fish‐food pellets (plant and animal biomass), bloodworms (animal biomass), and boiled white rice (plant carbohydrate), representing a balanced, protein‐rich, and protein‐poor diet, respectively. The TDF values of two “source amino acids” (Src‐AAs), methionine and phenylalanine, were close to zero (0.3–0.5‰) among the three diets, typifying the values reported in the literature (~0.5‰ and ~0.4‰, respectively). However, TDF values of “trophic amino acids” (Tr‐AAs) including alanine, valine, leucine, isoleucine, and glutamic acid varied by diet: for example, the glutamic acid TDF was similar to the standard value (~8.0‰) when tadpoles were fed either the commercial pellets (8.0‰) or bloodworms (7.9‰), but when they were fed boiled rice, the TDF was significantly reduced (0.6‰). These results suggest that a profound lack of dietary protein may alter the TDF values of glutamic acid (and other Tr‐AAs and glycine) within consumer species, but not the two Src‐AAs (i.e., methionine and phenylalanine). Knowledge of how a nutritionally poor diet can influence the TDF of Tr‐ and Src‐AAs will allow amino acid isotopic analyses to better estimate TP among free‐roaming animals. 相似文献
6.
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. 相似文献
7.
David W. Thieltges M. Anouk Goedknegt Katie O'Dwyer Alistair M. Senior Tsukushi Kamiya 《Oikos》2019,128(9):1329-1339
Stable isotopes are widely used to identify trophic interactions and to determine trophic positions of organisms in food webs. Comparative studies have provided general insights into the variation in isotopic composition between consumers and their diet (discrimination factors) in predator–prey and herbivore–plant relationships while other major components of food webs such as host–parasite interactions have been largely overlooked. In this study, we conducted a literature‐based comparative analysis using phylogenetically‐controlled mixed effects models, accounting for both parasite and host phylogenies, to investigate patterns and potential drivers in Δ13C and Δ15N discrimination factors in metazoan parasitic trophic interactions. Our analysis of 101 parasite–host pairs revealed a large range in Δ13C (–8.2 to 6.5) and Δ15N (–6.7 to 9.0) among parasite species, with no significant overall depletion or enrichment of 13C and 15N in parasites. As previously found in other trophic interactions, we identified a scaling relationship between the host isotopic value and both discrimination factors with Δ13C and Δ15N decreasing with increasing host δ13C and δ15N, respectively. Furthermore, parasite phylogenetic history explained a large fraction (>60%) of the observed variation in the Δ15N discrimination factor. Our findings suggest that the traditional isotope ecology framework (using an average Δ15N of 3.4‰) applies poorly to parasitic trophic interactions. They further indicate the need for a scaled rather than a fixed trophic discrimination factor framework along gradients of host δ15N. We also identified several conceptual and methodological issues which should to be considered in future research to help integrate parasitic interactions into a holistic isotope ecology framework across diverse trophic interactions. 相似文献
8.
Sarah Nahon Sarah Séité Sébastien Lefebvre Joanna Kolasinski Pierre Aguirre Inge Geurden 《Freshwater Biology》2020,65(11):1870-1882
- Using stable isotope ratios to explore the trophic ecology of freshwater animals requires knowledge about effects of food quality on isotopic incorporation dynamics. The aim of this experimental study was to: (1) estimate carbon and nitrogen isotopic incorporation rates and trophic discrimination factors (TDFs) of a freshwater first-feeding fish (i.e. salmonid fry) fed three diets that differed only in protein quality (animal or plant or a blend of both); (2) investigate effects of fasting and; (3) evaluate the proportion of each source assimilated when fry were fed a 50:50 animal:plant-based diet.
- For each diet, incorporation rates of δ13C and δ15N values were estimated using a time or growth-dependent isotopic incorporation model. Effects of fasting on isotope ratio values were measured regularly until the death of fry. Bayesian stable-isotope mixing models were used to estimate the contribution of animal and plant material to fish fed a blend of both food types.
- Our results show that incorporation rates were lower for fry fed a plant-based diet than for those fed an animal-based diet as growth rate decreased. Time- and growth-dependent models indicated that growth was solely responsible for isotopic incorporation in fry fed an animal-based diet, whereas catabolism increased in fry fed a plant-based diet. After lipid extraction, carbon TDFs were similar regardless of the diet, whereas nitrogen TDFs increased for fry fed a plant-based diet. Long-term fasting induced an increase of 0.63‰ in δ13C values of fry in 23 days, whereas δ15N values did not vary significantly. Proportions of food sources assimilated by fry fed an animal:plant-based diet were similar to those consumed when using a mixing model with the estimated TDFs, while proportions were unrealistic when using mean TDFs extrapolated from the literature.
- The results of our study indicate that the quality of food must be considered to use an appropriate timescale to detect changes in fry diets in the field. Moreover, we recommend using different carbon and nitrogen TDFs, one for animal-derived sources and one for plant-derived sources, to increase the accuracy of mixing models.
9.
Fujio Hyodo 《Entomological Science》2015,18(3):295-312
Insects are the most diverse organisms and often the most abundant animals in some ecosystems. Despite the importance of their functional roles and of the knowledge for conservation, the trophic ecology of many insect species is not fully understood. In this review, I present how stable carbon (C) and nitrogen (N) isotopes have been used to reveal the trophic ecology of insects over the last 30 years. The isotopic studies on insects have used differences in C isotope ratios between C3 and C4 plants, along vertical profiles of temperate and tropical forest stands, and between terrestrial and aquatic resources. These differences enable exploration of the relative importance of the food resources, as well as movement and dispersal of insects across habitats. The 13C‐enrichment (approximately 3‰) caused by saprotrophic fungi can allow the estimation of the importance of fungi in insect diets. Stable N isotopes have revealed food resource partitioning across diverse insect species above and belowground. Detritivorous insects often show a large trophic enrichment in 13C (up to 3‰) and 15N (up to 10‰) relative to the food substrates, soil organic matter. These values are greater than those commonly used for estimation of trophic level. This enrichment likely reflects the prevalence of soil microbial processes, such as fungal development and humification, influencing the isotopic signatures of diets in detritivores. Isotope analysis can become an essential tool in the exploration of insect trophic ecology in terms of biogeochemical C and N cycles, including trophic interactions, plant physiological and soil microbial processes. 相似文献
10.
Assimilation of carbon and nitrogen from pollen and nectar by a predaceous larva and its effects on growth and development 总被引:7,自引:0,他引:7
Joseph M. Patt Sam C. Wainright George C. Hamilton Dexter Whittinghill Keith Bosley Jan Dietrick James H. Lashomb 《Ecological Entomology》2003,28(6):717-728
Abstract. 1. Predaceous insects may benefit from feeding on non‐prey foods, such as pollen, nectar, and honeydew, because they can provide nutrients that help maintain metabolism and enhance overall nutrient intake. Yet, the extent to which predaceous insects can assimilate non‐prey food and the importance of diet mixing during particular life history stages is poorly understood. In this study the relative contribution of an omnivorous diet to the growth and survivorship of a predaceous larva was tested in a hypothetical situation in which nutritionally optimal prey was not available. The study system comprised a predaceous larva (second‐ and third‐instar larvae of the green lacewing Chrysoperla carnea), nutritionally poor prey (larvae of Drosophila melanogaster), and non‐prey food (pollen suspension, a mixture of bee pollen and artificial nectar (1 M sucrose solution)). Chrysoperla carnea larvae in the mixed diet treatment were provided with both Drosophila larvae and pollen suspension, while those reared on the prey and non‐prey diet treatments received only Drosophila larvae or pollen suspension respectively. 2. The inclusion of pollen and sucrose in their diet enhanced the growth of C. carnea larvae. Second instars reared on the mixed diet developed significantly faster than their cohorts reared on the prey diet, however third instars reared on the mixed diet did not develop faster than their cohorts reared on the prey diet. Larvae reared on the mixed diet became larger adults than did those reared on either the prey or non‐prey diets. Third instars reared on the non‐prey diet completed their development while second instars in the non‐prey diet treatment failed to pupate. 3. Stable isotope analysis indicated that the larvae obtained most of their carbon (55–73%) and nitrogen (71–73%) from Drosophila but acquired only a minor amount of carbon (2–5%) and nitrogen (3–11%) from pollen. Larvae reared on the mixed and non‐prey diets acquired a relatively significant amount of carbon (23–51%) from sucrose. 4. A model, which included a novel fractionation factor to account for the isotopic effect of metamorphosis, was developed to explain the proportion of larval growth attributable to each diet item. It explained the adult δ13C values to within 0.2‰ and adult δ15N values to within 0.7‰ in all treatments. 5. Adults fed 15N‐labelled pollen as larvae retained the 15N signal of the pollen as adults. 6. The collective results of this study support the view that, despite their dependence on prey arthropods to obtain most of their dietary nitrogen, omnivorous lacewing larvae can enhance their growth and development by supplementing their diets with alternative non‐prey food resources. This finding is consistent with the notion that omnivory has evolved as a feeding strategy to acquire both additional nitrogen as well as trace nutrients. 相似文献
11.
Alexandra L. Bloomfield Travis S. Elsdon Elizabeth J. Gier 《Journal of experimental marine biology and ecology》2011,399(1):48-59
Stable isotope ratios of carbon (δ13C) and nitrogen (δ15N) are widely used in food-web studies to determine trophic positioning and diet sources. However in order to accurately interpret stable isotope data the effects of environmental variability and dietary composition on isotopic discrimination factors and tissue turnover rates must be validated. We tested the effects of temperature and diet on tissue turnover rates and discrimination of carbon and nitrogen isotopes in an omnivorous fish, black bream (Acanthopagrus butcheri). Fish were raised at 16 °C or 23 °C and fed either a fish-meal or vegetable feed to determine turnover rates in fish muscle tissue up to 42 days after exposure to experimental treatments. Temperature and diet affected bulk tissue δ15N turnover and discrimination factors, with increased turnover and smaller discrimination factors at warmer temperatures. Fish reared on the vegetable feed showed greater bulk tissue δ15N changes and larger discrimination factors than those reared on a fish-meal feed. Temperature and diet affected bulk tissue δ13C values, however the direction of effects among treatments changed. Analyses of δ15N values of individual amino acids found few significant changes over time or treatment effects, as there was large variation at the individual fish level. However glutamic acid, aspartic acid and leucine changed most over the experiment and results mirrored those of treatment effects in bulk δ15N tissue values. The results demonstrate that trophic discrimination for δ15N and δ13C can be significantly different than those typically used in food-web analyses, and effects of diet composition and temperature can be significant. Precision of compound-specific isotope analyses (0.9‰) was larger than our effect size for bulk δ15N diet effects (0.7‰), therefore future experimental work in this area will need to establish a large effect size in order to detect significant differences. Our results also suggest that compound-specific amino acid δ15N may be useful for determining essential and non-essential amino acids for different animals. 相似文献
12.
T.C. O'Connell C.J. Kneale N. Tasevska G.G.C. Kuhnle 《American journal of physical anthropology》2012,149(3):426-434
The “trophic level enrichment” between diet and body results in an overall increase in nitrogen isotopic values as the food chain is ascended. Quantifying the diet–body Δ15N spacing has proved difficult, particularly for humans. The value is usually assumed to be +3–5‰ in the archaeological literature. We report here the first (to our knowledge) data from humans on isotopically known diets, comparing dietary intake and a body tissue sample, that of red blood cells. Samples were taken from 11 subjects on controlled diets for a 30‐day period, where the controlled diets were designed to match each individual's habitual diet, thus reducing problems with short‐term changes in diet causing isotopic changes in the body pool. The Δ15Ndiet‐RBC was measured as +3.5‰. Using measured offsets from other studies, we estimate the human Δ15Ndiet‐keratin as +5.0–5.3‰, which is in good agreement with values derived from the two other studies using individual diet records. We also estimate a value for Δ15Ndiet‐collagen of ≈6‰, again in combination with measured offsets from other studies. This value is larger than usually assumed in palaeodietary studies, which suggests that the proportion of animal protein in prehistoric human diet may have often been overestimated in isotopic studies of palaeodiet. Am J Phys Anthropol, 2012. © 2012 Wiley Periodicals, Inc. 相似文献
13.
A key factor for estimates of assimilation of resources and trophic position based on stable isotope data is the trophic discrimination factor (TDF). TDFs are assumed based on literature reviews, but may vary depending on a variety of factors, including the type of diet. We analyzed effects of alternative TDFs on estimates of assimilated resources and trophic positions for an omnivorous fish, Jenynsia multidentata, that reveals dietary variation among locations across a salinity gradient of a coastal lagoon in southern Brazil. We also compared estimates of foods ingested vs. foods assimilated. Food assimilation was estimated using carbon (δ13C) and nitrogen (δ15N) stable isotope ratios of food sources and consumer muscle tissue and an isotopic mixing model (SIAR); consumer trophic position (TP) was estimated from consumer and production source δ15N values. Diet was estimated using an index of relative importance based on frequency of occurrence and volumetric and numeric proportions of food items from stomach contents. The effect of variation in TDF on food assimilation and TP was tested using three alternative TDFs reported in review papers. We then created a new method that used food source-specific TDFs (reported separately for herbivores and carnivores) weighted in proportion to estimated assimilation of resources according to mixing model estimates to estimate TP (hereafter TPWAR). We found that plant material was not assimilated in a proportion similar to its importance in the diet of fish at a freshwater site, and the new method yielded best assimilation estimates. Animal material made greatest contributions to fish biomass irrespective of TDFs used in the mixing model. The new method produced TP estimates consistent with differences in estimated food assimilation along the salinity gradient. Our findings support the idea that food source-specific TDFs should be used in trophic studies of omnivores, since the method improved our ability to estimate trophic position and resource assimilation, two important ecological indicators. 相似文献
14.
Karen R. Crawley Glenn A. Hyndes 《Journal of experimental marine biology and ecology》2007,349(2):370-377
Discrimination of stable isotopes of carbon (δ13C) and nitrogen (δ15N) was examined for the amphipod Allorchestes compressa Dana using controlled laboratory experiments. Amphipods were fed exclusively on single diets (fresh or decomposed macroalgae or seagrass) for three weeks. Macrophyte type (i.e. seagrass, brown algae or red algae) had a greater influence on the stable isotope ratios of A. compressa than the state of decomposition of the macrophyte material. The experiments revealed that δ13C in A. compressa stabilised at values lower than those of the diets, which contrasts to the general assumption that consumer-diet discrimination of δ13C ranges from 0 to + 1‰. Amphipods fed on seagrass yielded the lowest δ13C values, which were 9 to 10‰ lower than their diet, while amphipods fed on macroalgae had values 2 to 4‰ lower than their diet. In addition, contrary to the general assumption that consumer-diet discrimination of δ15N ranges from + 3 to + 5‰, discrimination of δ15N was as low as − 1 and + 1 when A. compressa was fed on brown and red algae, respectively, but as high as + 3‰ when fed on seagrass. The results show that discrimination of stable isotopes of carbon and nitrogen can vary considerably depending on the food source, demonstrating that validation of assumptions about discrimination are critical for interpreting stable isotope data from field studies. 相似文献
15.
16.
Stable nitrogen (δ15N) and carbon (δ13C) isotopes of Atlantic sharpnose shark Rhizoprionodon terraenovae embryos and mothers were analysed. Embryos were generally enriched in 15N in all studied tissue relative to their mothers' tissue, with mean differences between mother and embryo δ15N (i.e. Δδ15N) being 1·4‰ for muscle, 1·7‰ for liver and 1·1‰ for cartilage. Embryo muscle and liver were enriched in 13C (both Δδ13C means = 1·5‰) and embryo cartilage was depleted (Δδ13C mean = ?1·01‰) relative to corresponding maternal tissues. While differences in δ15N and δ13C between mothers and their embryos were significant, muscle δ15N values indicated embryos to be within the range of values expected if they occupied a similar trophic position as their respective mothers. Positive linear relationships existed between embryo total length (LT) and Δδ15N for muscle and liver and embryo LT and Δδ13C for muscle, with those associations possibly resulting from physiological differences between smaller and larger embryos or differences associated with the known embryonic nutrition shift (yolk feeding to placental feeding) that occurs during the gestation of this placentatrophic species. Together these results suggest that at birth, the δ15N and δ13C values of R. terraenovae are likely higher than somewhat older neonates whose postpartum feeding habits have restructured their isotope profiles to reflect their postembryonic diet. 相似文献
17.
Rumiko Nakashita Yuzuru Hamada Eishi Hirasaki Juri Suzuki Toru Oi 《Primates; journal of primatology》2013,54(3):271-281
We determined the magnitude of isotopic fractionation of carbon and nitrogen stable isotope ratios (as enrichment factors, Δδ13C and Δδ15N, respectively) between the tissues and diets of captive Japanese macaques (Macaca fuscata) using a controlled feeding experiment, to provide basic data for reconstructing their feeding habits. The Δδ13C and Δδ15N values, respectively, were 0.9 ± 0.2 ‰ (mean ± standard deviation, SD) and 3.0 ± 0.3 ‰ for whole blood, 1.3 ± 0.2 ‰ and 4.3 ± 0.3 ‰ for plasma, and 0.8 ± 0.2 ‰ and 3.0 ± 0.2 ‰ for red blood cells. However, the Δδ13C and Δδ15N values for hair were 2.8 ± 0.3 ‰ and 3.4 ± 0.2 ‰, respectively. No difference was detected in the δ13C and δ15N values of hair sampled from different parts of the body. We investigated the effects of diet on δ13C in growing hair by alternating the diet of the macaques each month between two diets that differed markedly in δ13C. Hair regrown after shaving repeatedly recorded the δ13C of the diet consumed during the time of hair growth. On the other hand, hair naturally grown during the diet-change experiment did not show a clear pattern. One possible reason is that the hair had grown abnormally under unnatural indoor conditions and showed complicated isotope signatures. To reconstruct the long-term feeding history of Japanese macaques, we need to further clarify the relationships between the stable isotope signature of diet and various body tissues. 相似文献
18.
The use of stable isotopes to investigate animal diets, habitat use, and trophic level requires understanding the rate at
which animals incorporate the 13C and 15N from their diets and the factors that determine the magnitude of the difference in isotopic composition between the animal’s
diet and that of its tissues. We determined the contribution of growth and catabolic turnover to the rate of 13C and 15N incorporation into several tissues that can be sampled non-invasively (skin, scute, whole blood, red blood cells, and plasma
solutes) in two age classes of a rapidly growing ectotherm (loggerhead turtles, Caretta caretta). We found significant differences in C and N incorporation rates and isotopic discrimination factors (Δ13C = δ13Ctissues − δ13Cdiet and Δ15N = δ15Ntissues − δ15Ndiet) among tissues and between age classes. Growth explained from 26 to 100% of the total rate of incorporation in hatchling
turtles and from 15 to 52% of the total rate of incorporation in juvenile turtles. Because growth contributed significantly
to the rate of isotopic incorporation, variation in rates among tissues was lower than reported in previous studies. The contribution
of growth can homogenize the rate of isotopic incorporation and limit the application of stable isotopes to identify dietary
changes at contrasting time scales and to determine the timing of diet shifts. The isotopic discrimination factor of nitrogen
ranged from −0.64 to 1.77‰ in the turtles’ tissues. These values are lower than the commonly assumed average 3.4‰ discrimination
factors reported for whole body and muscle isotopic analyses. The increasing reliance on non-invasive and non-destructive
sampling in animal isotopic ecology requires that we recognize and understand why different tissues differ in isotopic discrimination
factors. 相似文献
19.
Stephen E. MacAvoy Alyssa Braciszewski Eric Tengi Daniel W. Fong 《Ecological Research》2016,31(4):589-595
In some environments, species may exhibit trophic plasticity, which allows them to extend beyond their assigned functional group. For Gammarus minus, a freshwater amphipod classified as a shredder or detritivore, cave populations have been observed consuming heterotrophs as well as shredding leaves, and therefore may be exhibiting trophic plasticity. To test this possibility, we examined the C and N stable isotope and C/N ratios for cave and spring populations of G. minus. A 15-day feeding experiment using leaves and G. minus from a spring population established that the diet-tissue discrimination factor was 3.2 ‰ for δ15N. Cave G. minus were 8 ‰ higher in δ15N relative to cave leaves, indicating they did not derive nitrogen from leaves, whereas field collected spring populations were 2–3 ‰ higher than spring leaves, indicating that they did. Cave G. minus were 2.6 ‰ higher in δ15N than the cave isopod, Caecidotea holsingeri. Relative to spring populations, Organ Cave G. minus were 15N enriched by 6 ‰, suggesting they occupied a different trophic level, or incorporated an isotopically distinct N source. While stable isotopes cannot tell what the cave G. minus are eating, the isotopes certainly show that G. minus are not eating leaves and are trophically distinct form the surface populations. Differences in C/N ratios were observed, but reflect the size of the G. minus examined and not feeding group or habitat. The isotope data strongly support the hypothesis that cave populations of G. minus have become generalist or omnivorous by including animal protein in their diet. 相似文献
20.
Does the proportion of arthropods versus fruit in the diet influence overwintering condition of an omnivorous songbird?
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Emily A. McKinnon T. Kurt Kyser Bridget J. M. Stutchbury 《Journal of Field Ornithology》2017,88(1):65-79
Many migratory songbirds switch from a primarily insectivorous diet during the breeding season to either a mixed diet or fruit diet during the non‐breeding season. However, for species with mixed diets, arthropods may be superior food items because of their higher protein content and easier digestibility. We tested this hypothesis by analyzing the diet and body condition of omnivorous Wood Thrushes (Hylocichla mustelina) at a non‐breeding site in tropical forest in Belize, Central America. We used analysis of stable isotopes δ15N and δ13C in the blood to measure diet. Our objective was to determine if a higher dietary proportion of arthropods relative to fruit (i.e., higher δ15N and δ13C) was associated with better body condition. We also examined the possible effect of age, sex, and habitat type on Wood Thrush diets, as well as any changes in diet through the overwintering period. We used a hierarchical Bayesian mixing model (MixSIAR) to estimate the proportion of different prey items in the diet of overwintering Wood Thrushes overall, in each habitat type, and over time during the non‐breeding period. From January to April, we found a significant decline in δ15N in forest habitats, whereas δ15N increased in scrub habitat. There was no significant seasonal change in δ13C. Birds with higher δ15N or δ13C values were not in better body condition. Females in dry‐scrub habitat consumed more fruit than males, but this did not affect body condition. Mixing model results indicated that most Wood Thrushes at our study sites consumed primarily arthropods, even during the driest times of the non‐breeding season and in the driest habitat. Overall, our results suggest that the diet of Wood Thrushes varies with habitat and during the overwintering period, but diet alone was not a predictor of body condition. Wood Thrushes, and possibly other omnivorous migratory songbirds, are apparently flexibly able to meet their wintering and pre‐migration nutritional demands with a variety of diets. 相似文献