Placing butterflies on the map – testing regional geographical resolution of three stable isotopes in Sweden using the monophagus peacock Inachis io

Stable isotope analyses of tissues have been used to help delineate natal regions and routes of migratory animals. The foundations of such studies are isotopic gradients or differences representing geographic regions and habitat used by the organism that are retained in selected tissues. We sampled peacock butterflies Inachis io on a regional level in southern Sweden to study natural variation and the resolving power of the stable isotope method to delineate individuals from known areas on a smaller scale than has typically been used in previous studies. Hydrogen (δD), carbon (δ¹³C) and nitrogen (δ¹⁵N) isotopes were obtained from butterflies at seven different locations in an area of 250×250 km over three years (2002–2004). We found sufficient isotopic differences on this regional scale to delineate approximate origins. Of the three isotopes, deuterium showed good discrimination between sites, carbon isotopes showed weaker differentiation, whereas nitrogen isotopes proved unsuitable for small scale studies in this region due to high and unpredictable variation. We found there was enough variation in δD between years to prevent a general application of the technique to resolve sub‐regional variation. Substantial part of this variation was probably caused by seasonal changes in δD of precipitation. These differences produce significant variation in δD between years in animals having short and variable tissue development times, and are difficult to estimate in natural situations. We conclude that stable isotopes are potentially powerful predictors for studies of migratory butterflies in Europe. However, without good knowledge about the sampled individuals’ previous life‐history, a lot of the natural environmental variation in tissue δD cannot be controlled for. In the case of migratory species, this information is difficult to obtain, making the confidence intervals for prediction of natal areas fairly wide and probably only suitable for longer distance migration.     

Tracing origins and migration of wildlife using stable isotopes: a review

To understand the ecology of migratory animals it is important to link geographic regions used by individuals including breeding, wintering, and intermediate stopover sites. Previous conventional approaches used to track animal movements have relied on extrinsic markers and typically the subsequent recovery of individuals. This approach has generally been inappropriate for most small, or non-game animals. The use of intrinsic markers such as fatty acid profiles, molecular DNA analyses, and the measurement of naturally occurring stable isotopes in animal tissues offer alternative approaches. This paper reviews the use of stable isotope analyses (primarily δ¹³C, δ¹⁵N, δ³⁴S, δD, δ⁸⁷Sr) to trace nutritional origin and migration in animals. This approach relies on the fact that foodweb isotopic signatures are reflected in the tissues of organisms and that such signatures can vary spatially based on a variety of biogeochemical processes. Organisms moving between isotopically distinct foodwebs can carry with them information on the location of previous feeding. Such an approach has been used to track animal use of inshore versus offshore, marine versus freshwater, terrestrial C₃ versus marine, terrestrial mesic versus xeric, and C₃ versus C₄ or Crassulacean acid metabolism foodwebs. More recently, the use of stable hydrogen isotope analyses (δD) to link organisms to broad geographic origin in North America is based on large-scale isotopic contours of growing-season average δD values in precipitation. This technique, especially when combined with the assay of other stable isotopes, will be extremely useful in helping to track migration and movement of a wide range of animals from insects to birds and mammals. Future research to refine our understanding of natural and anthropogenic-induced isotopic gradients in nature, and to explore the use of stable isotopes of other elements, is recommended. Received: 1 July 1998 / Accepted: 9 December 1998     

海洋动物档案式标志及其定位方法研究进展

档案式标志是一种可存储数据档案的电子标志,应用于水生动物尤其是大洋高度洄游性鱼类的研究,是获取海洋动物长时间、大空间尺度的活动信息和环境数据的有力工具.自20世纪90年代以来,档案式标志被大量用于海洋动物研究,取得了一系列成果,其不足之处在于需要回收标志来获取采样数据.90年代末,分离式卫星档案标志的问世解决了数据回收的问题,不再依赖于渔业捕捞,扩展了海洋动物研究的广度和深度.基于光亮度定位是研究海洋动物洄游路线的关键,其重点在于匹配光亮度与特定天顶角(如日出、日落),有3种方法：固定参照法、可变参照法和映射法.在过去的20年内,光亮度定位方法有所发展,并取得了一定的成果,但纬度向的定位还不够精确,有继续发展的空间.本文还总结了档案式标志定位的现存问题,展望了档案式标志及其定位方法的研究方向,并认为存在档案式标志小型化和传感器集成化、定位方法由单一光亮度反演向多因子反演的趋势.     

Stable isotopes can be used to infer the overwintering locations of prebreeding marine birds in the Canadian Arctic

Although assessments of winter carryover effects on fitness‐related breeding parameters are vital for determining the links between environmental variation and fitness, direct methods of determining overwintering distributions (e.g., electronic tracking) can be expensive, limiting the number of individuals studied. Alternatively, stable isotope analysis in specific tissues can be used as an indirect means of determining individual overwintering areas of residency. Although increasingly used to infer the overwintering distributions of terrestrial birds, stable isotopes have been used less often to infer overwintering areas of marine birds. Using Arctic‐breeding common eiders, we test the effectiveness of an integrated stable isotope approach (13‐carbon, 15‐nitrogen, and 2‐hydrogen) to infer overwintering locations. Knowing the overwinter destinations of eiders from tracking studies at our study colony at East Bay Island, Nunavut, we sampled claw and blood tissues at two known overwintering locations, Nuuk, Greenland, and Newfoundland, Canada. These two locations yielded distinct tissue‐specific isotopic profiles. We then compared the isotope profiles of tissues collected from eiders upon their arrival at our breeding colony, and used a k‐means cluster analysis approach to match arriving eiders to an overwintering group. Samples from the claws of eiders were most effective for determining overwinter origin, due to this tissue's slow growth rate relative to the 40‐day turnover rate of blood. Despite taking an integrative approach using multiple isotopes, k‐means cluster analysis was most effective when using 13‐carbon alone to assign eiders to an overwintering group. Our research demonstrates that it is possible to use stable isotope analysis to assign an overwintering location to a marine bird. There are few examples of the effective use of this technique on a marine bird at this scale; we provide a framework for applying this technique to detect changes in the migration phenology of birds' responses to rapid changes in the Arctic.     

Linking isotopic and migratory patterns in a pelagic seabird

The value of stable isotope analysis in tracking animal migrations in marine environments is poorly understood, mainly due to insufficient knowledge of isotopic integration into animal tissues within distinct water masses. We investigated isotopic and moult patterns in Cory’s shearwaters to assess the integration of different stable isotopes into feathers in relation to the birds’ transoceanic movements. Specimens of Mediterranean Cory’s shearwater Calonectris diomedea diomedea caught accidentally by Catalan longliners were collected and the signatures of stable isotopes of C (δ¹³C), N (δ¹⁵N) and S (δ³⁴S) were analysed in 11 wing and two tail feathers from 20 birds, and in some breast feathers. Based on isotopic signatures and moult patterns, the feathers segregated into two groups (breeding and wintering), corresponding to those grown in the Mediterranean or Atlantic regions, respectively. In addition, feathers grown during winter, i.e. moulted in Atlantic waters, were grouped into two isotopically distinct profiles, presumably corresponding to the two main wintering areas previously identified for Mediterranean Cory’s shearwater in tracking studies. N signatures mainly indicated the Mediterranean-to-Atlantic migration, whereas C and S signatures differed according to the Atlantic wintering area. Our results indicate that isotopic signatures from distant oceanic regions can integrate the feathers of a given bird and can indicate the region in which each feather was grown. This study thus underscores how stable isotope analysis can link marine animals to specific breeding and wintering areas, and thereby shed new light on studies involving assignment, migratory connectivity and carry-over effects in the marine environment. Xavier Ruiz deceased 27 April 2008.     

Zinc Isotope Ratios as Indicators of Diet and Trophic Level in Arctic Marine Mammals

Carbon and nitrogen stable isotope ratios of bone collagen are an established method for dietary reconstruction, but this method is limited by the protein preservation. Zinc (Zn) is found in bioapatite and the isotopic compositions of this element constitute a very promising dietary indicator. The extent of fractionation of Zn isotopes in marine environments, however, remains unknown. We report here on the measurement of zinc, carbon and nitrogen isotopes in 47 marine mammals from the archaeological site of Arvik in the Canadian Arctic. We undertook this study to test and demonstrate the utility of Zn isotopes in recent mammal bone minerals as a dietary indicator by comparing them to other isotopic dietary tracers. We found a correlation between δ⁶⁶Zn values and trophic level for most species, with the exception of walruses, which may be caused by their large seasonal movements. δ⁶Zn values can therefore be used as a dietary indicator in marine ecosystems for both modern and recent mammals.     

稳定性同位素技术与Keeling曲线法在陆地生态系统碳/水交换研究中的应用

稳定性同位素技术和Keeling曲线法是现代生态学研究的重要手段和方法之一。稳定性同位素能够整合生态系统复杂的生物学、生态学和生物地球化学过程在时间和空间尺度上对环境变化的响应。Keeling曲线法是以生物过程前后物质平衡理论为基础,将CO₂或H₂O的同位素组成(δD、δ¹³C或δ¹⁸O)与其对应浓度测量结合起来,将生态系统净碳通量区分为光合固定和呼吸释放通量,或将整个生态系统水分蒸散区分为植物蒸腾和土壤蒸发。在全球尺度上,稳定性同位素技术、Keeling曲线法与全球尺度陆地生态系统模型相结合,还可区分陆地生态系统和海洋生态系统对全球碳通量的贡献以及不同植被类型(C₃或C₄)在全球CO₂同化量中所占的比例。然而,生态系统的异质性使得稳定性同位素技术和Keeling曲线法从冠层尺度外推到生态系统、区域或全球尺度时存在有一定程度的不确定性。此外,取样时间、地点的选取也会影响最终的研究结果。尽管如此,随着分析手段的不断精确和研究方法的日趋完善,稳定性同位素技术和Keeling曲线法与其它测量方法(如微气象法)的有机结合将成为未来陆地生态系统碳/水交换研究的重要手段和方法之一。     

Effects of elemental composition on the incorporation of dietary nitrogen and carbon isotopic signatures in an omnivorous songbird

The use of stable isotopes to infer diet requires quantifying the relationship between diet and tissues and, in particular, knowing of how quickly isotopes turnover in different tissues and how isotopic concentrations of different food components change (discriminate) when incorporated into consumer tissues. We used feeding trials with wild-caught yellow-rumped warblers (Dendroica coronata) to determine delta15N and delta13C turnover rates for blood, delta15N and delta13C diet-tissue discrimination factors, and diet-tissue relationships for blood and feathers. After 3 weeks on a common diet, 36 warblers were assigned to one of four diets differing in the relative proportion of fruit and insects. Plasma half-life estimates ranged from 0.4 to 0.7 days for delta13C and from 0.5 to 1.7 days for delta15N . Half-life did not differ among diets. Whole blood half-life for delta13C ranged from 3.9 to 6.1 days. Yellow-rumped warbler tissues were enriched relative to diet by 1.7-3.6% for nitrogen isotopes and by -1.2 to 4.3% for carbon isotopes, depending on tissue and diet. Consistent with previous studies, feathers were the most enriched and whole blood and plasma were the least enriched or, in the case of carbon, slightly depleted relative to diet. In general, tissues were more enriched relative to diet for birds on diets with high percentages of insects. For all tissues, carbon and nitrogen isotope discrimination factors increased with carbon and nitrogen concentrations of diets. The isotopic signature of plasma increased linearly with the sum of the isotopic signature of the diet and the discrimination factor. Because the isotopic signature of tissues depends on both elemental concentration and isotopic signature of the diet, attempts to reconstruct diet from stable isotope signatures require use of mixing models that incorporate elemental concentration.     

Resolving temporal variation in vertebrate diets using naturally occurring stable isotopes

Assessments of temporal variation in diets are important for our understanding of the ecology of many vertebrates. Ratios of naturally occurring stable isotopes in animal tissues are a combination of the source elements and tissue specific fractionation processes, and can thus reveal dietary information. We review three different approaches that have been used to resolve temporal diet variation through analysis of stable isotopes. The most straightforward approach is to compare samples from the same type of tissue that has been sampled over time. This approach is suited to address either long or short-term dietary variation, depending on sample regime and which tissue that is sampled. Second, one can compare tissues with different metabolic rates. Since the elements in a given tissue have been assimilating during time spans specific to its metabolic rate, tissues with different metabolic rates will reflect dietary records over different periods. Third, comparisons of sections from tissues with progressive growth, such as hair, feathers, claws and teeth, will reveal temporal variation since these tissues will retain isotopic values in a chronological order. These latter two approaches are mainly suited to address questions regarding intermediate and short-term dietary variation. Knowledge of tissue specific metabolic rates, which determine the molecular turnover for a specific tissue, is of central importance for all these comparisons. Estimates of isotopic fractionation between source and measured target are important if specific hypotheses regarding the source elements are addressed. Estimates of isotopic fractionation, or at least of differences in fractionation between tissues, are necessary if different tissues are compared. We urge for more laboratory experiments aimed at improving our understanding of differential assimilation of dietary components, isotopic fractionation and metabolic routing. We further encourage more studies on reptiles and amphibians, and generally more studies utilizing multiple tissues with different turnover rates.     

Stable isotopes as tracers of organic matter input and transfer in benthic food webs: A review

Some of the ways that the application of stable isotopic tracers have contributed to the extremely hard task of understanding the energy and food web relations in benthic communities are illustrated in this review. Several methods are presented and their relative advantages are discussed, namely the use of endmembers, nitrogen isotopes, carbon isotopes, and sulfur isotopes. Special attention is given to the application of multiple tracers and transects sampling, natural and man-made perturbation experiments, and ¹⁵N additions as N cycle tracers.     

Stable sulphur isotopes in plants: a review

The determination of the natural abundances of stable isotopes has become a useful method by which to study the transformations of elements in biological and ecological studies as well as to investigate the mechanisms of chemical reactions. Unlike carbon and nitrogen isotopes, however, stable sulphur isotopes are used infrequently, and their potential as tracers in biochemical and physiological studies are only beginning to be realized. This review provides an overview of research involving stable sulphur isotopes in studies of plant metabolism and pollution. Topics discussed include the mechanisms and accompanying isotopic fractionations involved during the uptake and assimilation of inorganic sulphur compounds by plants, the utility of plants as bioindicators of environmental sulphur pollution, and the emission of isotopically light H₂S by plants in response to high concentations of sulphur. Future advances in the field are proposed.     

Multiple sources of isotopic variation in a terrestrial arthropod community: challenges for disentangling food webs

Documenting trophic links in a food web has traditionally required complex exclusion experiments coupled with extraordinarily labor-intensive direct observations of predator foraging. Newer techniques such as stable isotope analysis (SIA) may facilitate relatively quick and accurate assessments of consumer feeding behavior. Ratios of N and C isotopes are thought to be useful for determining species' trophic position (e.g., 1 degrees consumer, 2 degrees consumer, or omnivore) and their original carbon source (e.g., C3 or C4 plants; terrestrial or marine nutrients). Thus far, however, applications of stable isotopes to terrestrial arthropod food webs have suggested that high taxon-specific variation may undermine the effectiveness of this method. We applied stable isotope analysis to a pear orchard food web, in which biological control of a dominant pest, pear psylla (Cacopsylla pyricola), involves primarily generalist arthropod predators with a high frequency of omnivory. We found multiple sources of isotopic variation in this food web, including differences among plant tissues; time, stage, and taxon-specific differences among herbivores (despite similar feeding modes); and high taxon-specific variation among predators (with no clear evidence of omnivory). Collectively, these multiple sources of isotopic variation blur our view of the structure of this food web. Idiosyncrasies in consumer trophic shifts make ad hoc application of SIA to even moderately complex food webs intractable. SIA may not be a generally applicable "quick and dirty" method for delineating terrestrial food web structure-not without calibration of specific consumer food trophic shifts.     

Estimating niche width using stable isotopes in the face of habitat variability: a modelling case study in the marine environment

Distributions of stable isotopes have been used to infer an organism's trophic niche width, the 'isotopic niche', and examine resource partitioning. Spatial variation in the isotopic composition of prey may however confound the interpretation of isotopic signatures especially when foragers exploit resources across numerous locations. In this study the isotopic compositions from marine assemblages are modelled to determine the role of variation in the signature of prey items and the effect of dietary breadth and foraging strategies on predator signatures. Outputs from the models reveal that isotopic niche widths can be greater for populations of dietary specialists rather than for generalists, which contravenes what is generally accepted in the literature. When a range of different mixing models are applied to determine if the conversion from δ to p-space can be used to improve model accuracy, predator signature variation is increased rather than model precision. Furthermore the mixing models applied failed to correctly identify dietary specialists and/or to accurately estimate diet contributions that may identify resource partitioning. The results presented illustrate the need to collect sufficiently large sample sizes, in excess of what is collected under most current studies, across the complete distribution of a species and its prey, before attempts to use stable isotopes to make inferences about niche width can be made.     

Dietary variation in arctic foxes (Alopex lagopus)-an analysis of stable carbon isotopes

We used stable carbon isotopes to analyse individual variation in arctic fox diet. We extracted collagen from bones (the lower jaw), and measured stable carbon isotopes. The foxes came from three different localities: Iceland, where both microtines and reindeer are rare; west Greenland, where microtines are absent; and Sweden, where scat analyses showed the primary food to be microtine rodents and reindeer. The Icelandic samples included foxes from both coastal and inland habitats, the Swedish sample came from an inland area, and the Greenland sample from coastal sites. The spatial variation in the isotopic pattern followed a basic division between marine and terrestrial sources of protein. Arctic foxes from inland sites had ¹³C values of –21.4 (Iceland) and –20.4 (Sweden), showing typical terrestrial values. Coastal foxes from Greenland had typical marine values of –14.9, whereas coastal foxes from Iceland had intermediate values of –17.7. However, there was individual variation within each sample, probably caused by habitat heterogeneity and territoriality among foxes. The variation on a larger scale was related to the availability of different food items. These results were in accordance with other dietary analyses based on scat analyses. This is the first time that stable isotopes have been used to reveal individual dietary patterns. Our study also indicated that isotopic values can be used on a global scale.     

Physical and chemical basis of carbon isotope fractionation in plants

Naturally-occurring variations in the abundances of the stable isotopes of carbon and other elements can be used to understand the dynamics of natural processes in chemistry, biochemistry, biology, medicine, ecology and other fields. The use of carbon-13 isotopic abundances as an indicator of photosynthetic function in plants has become common. The purpose of this article is to describe the physical and chemical processes that contribute to the abundances of carbon-13 in plant materials, and to provide a framework for understanding how those processes control the isotopic contents of natural materials.     

Reconstruction of an aquatic food web: Viking Haithabu vs. Medieval Schleswig

In the last two decades, the analysis of stable isotopes of carbonate and collagen from archaeological bone finds became a useful tool in the reconstruction of ancient food webs. Nevertheless there is still only little information available about aquatic food webs, in particular concerning brackish water ecosystems. The Schlei Fjord in Schleswig-Holstein, Germany, is such an ecosystem and was investigated to determine stable isotopic values for nitrogen, carbon and oxygen from bone collagen and carbonate in archaeological bone finds. Wild birds, mammals and fish bones from the Viking settlement Haithabu and the medieval town of Schleswig have been analyzed in this study to determine stable isotope values for marine and limnic species and to investigate possible isotopic gradients for mixing fresh water and salt water ecosystems.     

Role of stable isotopes in life--testing isotopic resonance hypothesis

Stable isotopes of most important biological elements, such as C, H, N and O, affect living organisms. In rapidly growing species, deuterium and to a lesser extent other heavy isotopes reduce the growth rate. At least for deuterium it is known that its depletion also negatively impacts the speed of biological processes. As a rule, living organisms "resist" changes in their isotopic environment, preferring natural isotopic abundances. This preference could be due to evolutionary optimization; an additional effect could be due to the presence of the "isotopic resonance". The isotopic resonance phenomenon has been linked to the choice of earliest amino acids, and thus affected the evolution of genetic code. To test the isotopic resonance hypothesis, literature data were analyzed against quantitative and qualitative predictions of the hypothesis. Four studies provided five independent datasets, each in very good quantitative agreement with the predictions. Thus, the isotopic resonance hypothesis is no longer simply plausible; it can now be deemed likely. Additional testing is needed, however, before full acceptance of this hypothesis.     

同位素富集-稀释法研究食性转变对鱼类不同组织N同位素转化率的影响

稳定同位素技术广泛地用于描绘生态系统中食物网的食物来源和营养级关系,但是消费者不同组织转化率的研究相对较少。通过锦鲤摄食人工添加15N蓝藻的食性转化实验,研究不同组织N同位素转化率的差异,探讨组织生长和代谢对同位素转化的相对贡献,为不同时间尺度的稳定同位素研究取样奠定基础。结果表明,通过42d的加富蓝藻饲喂,各组织的N稳定同位素发生显著变化。肝的δ15N为(19.3±1.4)‰,显著高于其它组织,其次为鱼鳍((15.6±1.0)‰)和血液((12.6±0.4)‰),肌肉的δ15N‰最低,为(9.9±0.7)‰。在随后的同位素稀释实验中,锦鲤的体重增加,相对生长速率为0.011d-1,鳍肉的转化率最快,达到11.4%/d,半衰期仅为6.1d,其次是血液和肝,肌肉的转化率最低,仅有3.8%/d,半衰期最长,为18.4d。代谢衰减指数c和-1不存在显著差异,表明锦鲤各组织的N同位素转化主要由组织生长引起。结论显示,同位素富集-稀释法可以有效评价鱼类食性转变对不同组织同位素转化的差异,鳍肉和血液同位素分析可以作为锦鲤食性转变快速追踪的手段。     

15N自然丰度法在生态系统氮素循环研究中的应用

稳定性同位素技术是现代生态学研究中的一门新兴技术,在生态学研究的诸多领域都展示了广阔的应用前景,其中,稳定性同位素＾１５Ｎ自然丰度法近年来在生态系统氮素循环研究中发挥了正在发挥着极为重要的作用,首先简述了自然生态系统氮素循环诸过程中的＾１５Ｎ同位素分馏机制,然后,在此基础上,综述了＾１５Ｎ自然丰度法的基本原理与方法,列举了近年 来此法在生物固氮及氮素转化过程研究中的一些应用实例,并预测了该方法在国     

Isotopic randomness as a biological factor

We discuss an alternative source of randomness originating at the atomic level due to the diversity of stable isotopes. This randomness could contribute to mutation mechanisms through atomic scale variations of bond lengths and strengths, differences in the reaction rates, etc. In terms of purposeful experimentation, isotopic replacements in living organisms give an independent parametrization which allows correlation of global biological variables with the level of individual atoms. We review the work done so far, and suggest some further experimental possibilities by analogy with some isotopic effects and isotopic structuring in solid state physics.