首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 9 毫秒
1.
2.
The differential discrimination of nitrogen isotopes (15N/14N) within amino acids in consumers and their diets has been routinely used to estimate organismal tropic position (TP). Analogous isotopic discrimination can occur within plants, particularly in organs lacking chloroplasts. Such discrimination likely arises from the catabolic deamination of amino acids, resulting in a numerical elevation of estimated TP, within newly synthesized biomass. To investigate this phenomenon, we examined the 15N/14N of amino acids (δ15NAA) in spring leaves and flowers from eight deciduous and two annual plants. These plants were classified on the basis of their time of bloom, plants that bloomed when their leaves were absent (Type I) versus plants that bloomed while leaves were already present (Type II). Based on the δ15NAA values from leaves, both plant types occupied comparable and ecologically realistic mean TPs (=1.0 ± 0.1, mean ± 1σ). However, the estimated TPs of flowers varied significantly (Type I: 2.2 ± 0.2; Type II: 1.0 ± 0.1). We hypothesize that these results can be interpreted by the following sequence of events: (1) Type I floral biomass is synthesized in absence of active photosynthesis; (2) the catabolic deamination of amino acids in particular, leaves behind 15N in the residual pool of amino acids; and (3) the incorporation of these 15N‐enriched amino acids within the biomass of Type I flowers results in the numerical elevation of the TPs. In contrast, the actively photosynthesizing Type II leaves energetically sustain the synthesis of Type II flower biomass, precluding any reliance on catabolic deamination of amino acids. Amino acids within Type II flowers are therefore isotopically comparable to the Type II leaves. These findings demonstrate the idiosyncratic nature of the δ15NAA values within autotrophic organs and have implications for interpreting trophic hierarchies using primary producers and their consumers.  相似文献   

3.
稳定性同位素技术在生态学上的应用   总被引:11,自引:2,他引:9  
稳定性同位素技术早在20世纪70年代末期就被引入到生态学领域。最初是利用植物稳定性碳同位素的差异。开展了许多有关营养流动方面的研究;到90年代,稳定性碳和氮同位素被用来分析动物的食性、营养级位置关系以及食物链结构;本世纪初,由于技术的进步,稳定性同位素(特别是氢同位素)被用来开展动物迁徙习性方面的研究。到目前为止,国内有关这方面的研究还鲜有报道,而且对自然界存在的稳定性同位素的理解还存在一定偏差。本文主要介绍了稳定性同位素效应及其分馏原理、稳定性同位素在示踪动物食性信息、确定营养级位置关系、分析食物网结构以及研究动物迁徙生态学中的作用等方面的内容。  相似文献   

4.
5.
It is difficult to separate an age-dependent fall in nitrogen use efficiency (NUE; N balance/N intake) in growing ruminants from a progressively decrease in animal protein requirements over time. This study examined the effect of dietary protein content on N partitioning, digestibility and N isotopic discrimination between the animal and its diet (Δ15Nanimal-diet) evaluated at two different fattening periods (early v. late). Twenty-four male Romane lambs (age: 19 ± 4.0 days; BW: 8.3 ± 1.39 kg) were equally allocated to three dietary CP treatments (15%, 17% and 20% CP on a DM basis). Lambs were reared with their mothers until weaning, thereafter housed in individual pens until slaughter (45 kg BW). During the post-weaning period, lambs were allocated twice (early fattening (30 days post-weaning) and late fattening (60 days post-weaning)) to metabolic cages for digestibility and N balance study. When diet CP content increased, the average daily gain of lambs increased (P < 0.05) while the age at slaughter decreased (P = 0.01), but no effect was observed on feed efficiency (P > 0.10). Diet CP content had limited effect on lamb carcass traits. Higher fibre digestibility was observed at the early v. late fattening period (P < 0.001). The N intake and the urinary N excretion increased when diet CP content increased (P < 0.001) and when shifting from early to late fattening period (P < 0.001). Faecal N excretion (P = 0.14) and N balance (P > 0.10) were not affected by diet CP content. Nitrogen digestibility increased (P < 0.001) as the diet CP content increased and on average it was greater at late v. early fattening period (P = 0.02). The NUE decreased (P = 0.001) as the diet CP content increased and as the lamb became older (P < 0.001). However, the age-dependent fall in NUE observed was lower at high v. low dietary CP content (CP × age interaction; P = 0.04). The Δ15Nanimal-diet was positively correlated (P < 0.05) with N intake (r = 0.59), excretion of faecal N (r = 0.41), urinary N (r = 0.69) and total manure N (r = 0.64), while negatively correlated with NUE (r = −0.57). Overall, the experiment showed NUE was lower in older lambs and when lambs were fed high diet CP content, and that Δ15Nanimal-diet was a useful indicator not only for NUE but also for urinary N excretion, which is a major environmental pollution factor on farm.  相似文献   

6.
The abundance and biomass of benthic foraminifera are high in intertidal rocky‐shore habitats. However, the availability of food to support their high biomass has been poorly studied in these habitats compared to those at seafloor covered by sediments. Previous field and laboratory observations have suggested that there is diversity in the food preferences and modes of life among rocky‐shore benthic foraminifera. In this study, we used the stable nitrogen isotopic composition of amino acids to estimate the trophic position, trophic niche, and feeding strategy of individual foraminifera species. We also characterized the configuration and structure of the endobiotic microalgae in foraminifera using transmission electron microscopy, and we identified the origin of endobionts based on nucleotide sequences. Our results demonstrated a large variation in the trophic positions of different foraminifera from the same habitat, a reflection of endobiotic features and the different modes of life and food preferences of the foraminifera. Foraminifera did not rely solely on exogenous food sources. Some species effectively used organic matter derived from endobionts in the cell cytoplasm. The high biomass and species density of benthic foraminifera found in intertidal rocky‐shore habitats are thus probably maintained by the use of multiple nitrogen resources and by microhabitat segregation among species as a consequence.  相似文献   

7.
8.
The stable isotope compositions (C and N) of plants and animals of a marsh dominated by Spartina alterniflora in the Delaware Estuary were determined. The study focused on the juvenile stage of the Atlantic blue crab, Callinectes sapidus, and the importance of marsh-derived diets in supporting growth during this stage. Laboratory growth experiments and field data indicated that early juvenile blue crabs living in the Delaware Bay habitat fed primarily on zooplankton, while marsh-dwelling crabs, which were enriched in 13C relative to bay juveniles, utilized marsh-derived carbon for growth. In laboratory experiments, the degree to which juvenile blue crabs isotopically fractionated dietary nitrogen, as well as the growth rate, depended on the protein quality of the diet. The range of δ13C of amino acids in laboratory-reared crabs and their diets was almost 20‰, similar to the isotopic range of amino acids of other organisms. In laboratory studies, the δ13C of nonessential and essential amino acids in the diet were compared to those in juvenile crabs. Isotopic fractionation at the molecular level depended on diet quality and the crabs' physiological requirements. Comparison of whole-animal isotope data with individual amino acid C isotope measurements of wild juvenile blue crabs from the bay and marsh suggested a different source of total dietary carbon, yet a shared protein component, such as zooplankton. Received: 1 July 1998 / Accepted: 15 March 1999  相似文献   

9.
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   

10.
Summary By application with 2-aminoethanol (2-AE) and choline chloride (CC) in pot experiments the effect of drought stress on barley plants was diminished. In treated plants an increase of the grain yield by 14% (2-AE) and 40% (CC) and a decrease of the stress metabolites glycine betaine and trigonelline was observed. Additionally, treated barley plants showed higher yields of essential amino acids as well. The contents of proline (stress indicator) and arginine (precursor of the stress metabolite putrescine) of treated plants were by 12% and 22% respectively, lower than in untreated plants.  相似文献   

11.
  1. Stable isotope mixing models (SIMMs) are widely used for characterizing wild animal diets. Such models rely upon using accurate trophic discrimination factors (TDFs) to account for the digestion, incorporation, and assimilation of food. Existing methods to calculate TDFs rely on controlled feeding trials that are time-consuming, often impractical for the study taxon, and may not reflect natural variability of TDFs present in wild populations.
  2. We present TDFCAM as an alternative approach to estimating TDFs in wild populations, by using high-precision diet estimates from a secondary methodological source—in this case nest cameras—in lieu of controlled feeding trials, and provide a framework for how and when it should be applied.
  3. In this study, we evaluate the TDFCAM approach in three datasets gathered on wild raptor nestlings (gyrfalcons Falco rusticolus; peregrine falcons Falco perigrinus; common buzzards Buteo buteo) comprising contemporaneous δ13C & δ15N stable isotope data and high-quality nest camera dietary data. We formulate Bayesian SIMMs (BSIMMs) incorporating TDFs from TDFCAM and analyze their agreement with nest camera data, comparing model performance with those based on other relevant TDFs. Additionally, we perform sensitivity analyses to characterize TDFCAM variability, and identify ecological and physiological factors contributing to that variability in wild populations.
  4. Across species and tissue types, BSIMMs incorporating a TDFCAM outperformed any other TDF tested, producing reliable population-level estimates of diet composition. We demonstrate that applying this approach even with a relatively low sample size (n < 10 individuals) produced more accurate estimates of trophic discrimination than a controlled feeding study conducted on the same species. Between-individual variability in TDFCAM estimates for ∆13C & ∆15 N increased with analytical imprecision in the source dietary data (nest cameras) but was also explained by natural variables in the study population (e.g., nestling nutritional/growth status and dietary composition).
  5. TDFCAM is an effective method of estimating trophic discrimination in wild animal populations. Here, we use nest cameras as source dietary data, but this approach is applicable to any high-accuracy method of measuring diet, so long as diet can be monitored over an interval contemporaneous with a tissue's isotopic turnover rate.
  相似文献   

12.
Compound‐specific stable isotope analysis (CSIA) of amino acids (AA) has rapidly become a powerful tool in studies of food web architecture, resource use, and biogeochemical cycling. However, applications to avian ecology have been limited because no controlled studies have examined the patterns in AA isotope fractionation in birds. We conducted a controlled CSIA feeding experiment on an avian species, the gentoo penguin (Pygoscelis papua), to examine patterns in individual AA carbon and nitrogen stable isotope fractionation between diet (D) and consumer (C) (Δ13CC‐D and Δ15NC‐D, respectively). We found that essential AA δ13C values and source AA δ15N values in feathers showed minimal trophic fractionation between diet and consumer, providing independent but complimentary archival proxies for primary producers and nitrogen sources respectively, at the base of food webs supporting penguins. Variations in nonessential AA Δ13CC‐D values reflected differences in macromolecule sources used for biosynthesis (e.g., protein vs. lipids) and provided a metric to assess resource utilization. The avian‐specific nitrogen trophic discrimination factor (TDFGlu‐Phe = 3.5 ± 0.4‰) that we calculated from the difference in trophic fractionation (Δ15NC‐D) of glutamic acid and phenylalanine was significantly lower than the conventional literature value of 7.6‰. Trophic positions of five species of wild penguins calculated using a multi‐TDFGlu‐Phe equation with the avian‐specific TDFGlu‐Phe value from our experiment provided estimates that were more ecologically realistic than estimates using a single TDFGlu‐Phe of 7.6‰ from the previous literature. Our results provide a quantitative, mechanistic framework for the use of CSIA in nonlethal, archival feathers to study the movement and foraging ecology of avian consumers.  相似文献   

13.
1. A comparative study of fatty acid (FA) profiles in particulate matter (seston) and the key grazer Daphnia was performed in six high Arctic ponds (79°N, Svalbard). The ponds were all small and shallow, but followed a strong gradient with respect to nutrient content and optical properties. 2. A distinct locality‐specific pattern was detected by principal component analysis of FA profiles, where samples from each locality clustered both with regard to seston and Daphnia. Linear discriminant analysis using nine sestonic fatty acids as discriminant functions gave on average a correct prediction of the Daphnia lake membership in 47% of cases, with very high predictability in some lakes but poor predictability in others. 3. No significant correlation was detected between FA and nutrient concentration or levels of dissolved organic carbon. The major determinant of FA profiles as judged from a redundancy analysis was the taxonomic composition of phytoplankton communities, notably the biomass of Chlorophyceae. 4. The FA profiles of Daphnia were for some FAs strongly enriched relative to the seston, while diluted for others. Among the polyunsaturated fatty acids (PUFAs), a pronounced magnification of eicosapentaenoic acid (EPA, 20 : 5 n‐3), and to some extent 18 : 3 n‐3 and 20 : 4 n‐6 was found, while docosahexaenoic acid (DHA, 22 : 6 n‐3) contributed in general less to FAs in Daphnia than in seston and was hardly detectable in Daphnia from most localities. 5. The overall content of PUFAs in Daphnia was consistently high, close to 40% of total FA in all investigated localities, despite major differences in seston PUFA content. Daphnia thus acts as a regulator with regard to overall PUFAs, reflecting its physiological constraints and relatively fixed demands for PUFAs in general. The distinct locality‐specific profiles in Daphnia strongly suggest a kind of FA‐fingerprint, but our data do not allow strict statements on the use of specific FAs as trophic markers.  相似文献   

14.
The food habits of the endangered giant water bug, Lethocerus deyrolli, were studied in the rice fields of Nose, in the north of Osaka Prefecture, Japan. Field observations revealed that frogs were the most important prey item. Frogs represented 86.4% and 78.6% in the diet of L. deyrolli in spring and summer, respectively. Among seven species of three families (Hylidae, Rhacophoridae, and Ranidae) exploited by L. deyrolli, the most important food item was adult Hyla japonica in spring and juvenile Rana nigromaculta in summer. Fish and aquatic arthropods were not considered important foods for L. deyrolli. The frog‐dependent food habits indicate that the recovery and conservation of frogs should be prioritized to protect L. deyrolli from extinction.  相似文献   

15.
本研究在原来CASA模型的基础上,对模型参数最大光能利用率和水分胁迫系数的算法进行了改进,利用改进后的CASA模型模拟了2010年内蒙古锡林郭勒盟草原植被净初级生产力(NPP),并用地面实测样方数据对改进后的模型进行精度验证。结果表明:改进的CASA模型可应用于内蒙古草原小尺度植被NPP的估测,模拟NPP值与地面实测值之间的相关性达到显著水平(R2=0.829,P0.05);2010年内蒙古锡林郭勒盟草原植被生长季(4—10月)NPP为284.64 g C·m-2·a-1,不同地区年均NPP相差较大,东北部东乌珠穆沁旗草原NPP高达411.11 g C·m-2·a-1,而西北部的二连浩特市草原NPP仅为158.87 g C·m-2·a-1;整体上,锡林郭勒盟草原的NPP由东向西逐步递减,这与该区域水热条件限制基本一致;由于降水量的时滞效应,该年度内NPP出现两次峰值;2010年锡林郭勒境内草原NPP集中分布在250~350 g C·m-2·a-1,草甸草原的NPP最大,典型草原次之,荒漠草原最小。  相似文献   

16.
新疆准噶尔盆地荒漠草地水源圈植物群落退化格局   总被引:1,自引:0,他引:1  
游牧民定居放牧是目前主要的放牧方式,导致水源圈在中国北方干旱半干旱区草场上普遍存在。2014年5月底至6月初,在新疆北部荒漠草地上,以一个典型的牧场水源点为中心,在8个方向上设置50、100、200、400、800和1200 m共6个采样距离进行植物群落调查取样。通过分析植物群落的组成、物种重要值、丰富度以及群落的盖度、高度和地上生物量的变化特征,期望为荒漠草地退化生态系统的恢复和可持续管理提供科学依据。结果表明:随着与水源点距离的减少、放牧强度的增加,荒漠草地植物群落特征呈现明显梯度变化,建群植物博洛塔绢蒿优势度逐渐降低,1年生植物优势度逐渐增加;植物群落、多年生草本植物和1年生草本植物的物种丰富度逐渐增加;群落总盖度逐渐降低,与建群植物博洛塔绢蒿的盖度显著正相关。1年生植物和有毒植物骆驼蓬在水源点附近优势度增加,说明放牧导致水源点附近地上植物群落趋于退化。因此,在这一地区开展游牧民定居导致水源圈大量出现,可能加剧荒漠草地的退化。  相似文献   

17.
崂山湾人工鱼礁区星康吉鳗摄食生态及食物网结构   总被引:2,自引:0,他引:2  
根据2015年4月至2017年1月于崂山湾人工鱼礁区地笼网和延绳钓捕获的279尾星康吉鳗样本,从胃含物组成、食性类型、摄食等级、营养生态位和营养级等方面对其摄食生态进行研究,同时结合海区许氏平鲉、大泷六线鱼、斑头鱼、褐菖鲉、花鲈等9种鱼类的胃含物分析结果,构建人工鱼礁区鱼类关键种的简化食物网模型.食性研究结果表明:星康吉鳗共摄食7类30余种饵料,虾类是其最主要的饵料类群,其次为鱼类和头足类,大泷六线鱼、方氏云鳚、鹰爪虾、玉筋鱼和日本鼓虾等是其优势饵料.星康吉鳗的饵料生物组成随肛长和季节发生显著变化.四季均以鱼类和虾类为主,春季胃含物中包括头足类,秋季包括头足类和蟹类,冬季亦有蟹类出现.肛长≤120 mm的星康吉鳗主要摄食鱼卵和鹰爪虾,120~130 mm肛长组主要摄食玉筋鱼和日本鼓虾,肛长>130 mm的星康吉鳗主要摄食大泷六线鱼和方氏云鳚.其摄食强度也随季节和肛长而变化,空胃率的季节性差异显著,平均胃饱满系数的季节性差异不显著,不同肛长组的空胃率和平均胃饱满系数均不存在显著差异.人工鱼礁区简化食物网结构显示:鱼类关键种的营养级均在3级以上,星康吉鳗的营养级为4.636,处于海区食物网的最顶端.虾类、蟹类、端足类和软体动物等是鱼类关键种的主要饵料,甲壳类、方氏云鳚、大泷六线鱼和玉筋鱼是高营养级鱼类花鲈和星康吉鳗的主要饵料.  相似文献   

18.
Nitrogen stable isotopes analysis of individual bone collagen amino acids was applied to archeological samples as a new tool for assessing the composition of ancient human diets and calibrating radiocarbon dates. We used this technique to investigate human and faunal samples from the Kitakogane shell midden in Hokkaido, Japan (5,300–6,000 cal BP). Using compound‐specific nitrogen isotope analysis of individual amino acids, we aimed to estimate i) the quantitative contribution of marine and terrestrial protein to the human diet, and ii) the mean trophic level (TL) from which dietary protein was derived from marine ecosystems. Data were interpreted with reference to the amino acid trophic level (TLAA) model, which uses empirical amino acid δ15N from modern marine fauna to construct mathematical equations that predict the trophic position of organisms. The TLAA model produced realistic TL estimates for the Kitakogane marine animals. However, this model was not appropriate for the interpretation of human amino acid δ15N, as dietary protein is derived from both marine and terrestrial environments. Hence, we developed a series of relevant equations that considered the consumption of dietary resources from both ecosystems. Using these equations, the mean percentage of marine protein in the Kitakogane human diet was estimated to be 74%. Although this study is one of the first systematic investigations of amino acid δ15N in archeological bone collagen, we believe that this technique is extremely useful for TL reconstruction, palaeodietary interpretation, and the correction of marine reservoir effects for radiocarbon dating. Am J Phys Anthropol 143:31–40, 2010. © 2010 Wiley‐Liss, Inc.  相似文献   

19.
The common usage of protein-free diets to estimate unspecific AA losses has been criticised as unphysiological and incorrect. Therefore, in this study different diets were tested for the determination of endogenous losses (EL) of amino acids (AA) and nitrogen (N) assuming a complete absorption in the small intestine. Seven cannulated gilts received a protein-free diet (Diet PF) or diets with 3%, 6% or 10% crude protein (CP) from crystalline AA (Diets CA) or casein (Diets CAS) according to a 7 × 7 Latin square design. After 6 d adaptation to the diet, ileal digesta was collected for 24 h and thereafter analysed for AA, N and the digestibility markers Cr2O3 and acid insoluble ash (AIA). Generally, among all AA, the highest amounts of EL were found for Pro, Glu and Gly, and the smallest for Met. Different levels of CP in Diets CA and CAS had no effect on EL. Significant differences between treatments were observed only for the EL of Glu, Ile, Ser (higher in Diets CA and PF), Pro and Tyr (higher in Diet PF) (p < 0.05). There were no differences in determined EL using Cr2O3 or AIA as digestibility markers.  相似文献   

20.
Compound‐specific stable isotope analysis (CSIA) of amino acids (AAs) has been rapidly incorporated in ecological studies to resolve consumer trophic position (TP). Differential 15N fractionation of “trophic” AAs, which undergo trophic 15N enrichment, and “source” AAs, which undergo minimal trophic 15N enrichment and serve as a proxy for primary producer δ15N values, allows for internal calibration of TP. Recent studies, however, have shown the difference between source and trophic AA δ15N values in higher marine consumers is less than predicted from empirical studies of invertebrates and fish. To evaluate CSIA‐AA for estimating TP of cetaceans, we compared source and trophic AA δ15N values of multiple tissues (skin, baleen, and dentine collagen) from five species representing a range of TPs: bowhead whales, beluga whales, short‐beaked common dolphins, sperm whales, and fish‐eating (FE) and marine mammal‐eating (MME) killer whale ecotypes. TP estimates (TPCSIA) using several empirically derived equations and trophic discrimination factors (TDFs) were 1–2.5 trophic steps lower than stomach content‐derived estimates (TPSC) for all species. Although TPCSIA estimates using dual TDF equations were in better agreement with TPSC estimates, our data do not support the application of universal or currently available dual TDFs to estimate cetacean TPs. Discrepancies were not simply due to inaccurate TDFs, however, because the difference between consumer glutamic acid/glutamine (Glx) and phenylalanine (Phe) δ15N values (δ15NGlx‐Phe) did not follow expected TP order. In contrast to pioneering studies on invertebrates and fish, our data suggest trophic 15N enrichment of Phe is not negligible and should be examined among the potential mechanisms driving “compressed” and variable δ15NGlx‐Phe values at high TPs. We emphasize the need for controlled diet studies to understand mechanisms driving AA‐specific isotopic fractionation before widespread application of CSIA‐AA in ecological studies of cetaceans and other marine consumers.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号