Environmental and Physiological Influences to Isotopic Ratios of N and Protein Status in a Montane Ungulate in Winter

Gustine, David D.; Barboza, Perry S.; Adams, Layne G.; Wolf, Nathan

doi:10.1371/journal.pone.0103471

Cited by 8 publications

(11 citation statements)

References 73 publications

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“…We corroborate the conclusion of Woodland et al [ 8 ] that temporally dynamic isotopic baselines should be investigated prior to the application of stable isotopes in ecology, to avoid biased conclusions on trophic relationships. Stable isotope analysis is currently used to provide answers to a wide range of questions on diet and foraging strategies [ 87 – 89 ], migration [ 90 – 92 ], physiology [ 93 ], host-parasite interactions [ 94 ], wildlife management [ 95 ] and conservation of threatened species [ 96 ], among others. To improve the predictive precision of this technology, further research on how consumers integrate changes in ecosystem isotopic values over different time scales is needed.…”

Section: Discussionmentioning

confidence: 99%

Seasonal Variation in Stable Carbon and Nitrogen Isotope Values of Bats Reflect Environmental Baselines

et al. 2015

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The stable carbon and nitrogen isotope composition of animal tissues is commonly used to trace wildlife diets and analyze food chains. Changes in an animal’s isotopic values over time are generally assumed to indicate diet shifts or, less frequently, physiological changes. Although plant isotopic values are known to correlate with climatic seasonality, only a few studies restricted to aquatic environments have investigated whether temporal isotopic varia-tion in consumers may also reflect environmental baselines through trophic propagation. We modeled the monthly variation in carbon and nitrogen isotope values in whole blood of four insectivorous bat species occupying different foraging niches in southern Spain. We found a common pattern of isotopic variation independent of feeding habits, with an overall change as large as or larger than one trophic step. Physiological changes related to reproduction or to fat deposition prior to hibernation had no effect on isotopic variation, but juvenile bats had higher δ13C and δ15N values than adults. Aridity was the factor that best explained isotopic variation: bat blood became enriched in both 13C and 15N after hotter and/or drier periods. Our study is the first to show that consumers in terrestrial ecosystems reflect seasonal environmental dynamics in their isotope values. We highlight the danger of misinterpreting stable isotope data when not accounting for seasonal isotopic baselines in food web studies. Understanding how environmental seasonality is inte-grated in animals’ isotope values will be crucial for developing reliable methods to use stable isotopes as dietary tracers.

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Section: Discussionmentioning

confidence: 99%

Seasonal Variation in Stable Carbon and Nitrogen Isotope Values of Bats Reflect Environmental Baselines

et al. 2015

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“…Therefore, using only bulk δ 15 N to assign the TP will leave a large amount of uncertainty regarding the actual dietary relationships. An accurate explanation of the bulk δ 15 N records demands a rigorous understanding of the biochemical and physiological effects on nitrogen metabolism (Boecklen et al ; Gustine et al ).…”

Section: βCorr and The Contribution Of Vascular Plant As A Diet Resoumentioning

confidence: 99%

“…These studies suggested that the TEF value is variable and usually lower than 7.6‰ and indicated that a single TEF value is unlikely to realize the full potential of the CSIA‐AA method applied to assess trophic ecology (Blanke et al ; O'Connell ). The large variations of TEF values are driven by two biochemical factors, i.e., the feeding ecology and nitrogen excretion mode, which makes it the most sensitive parameter for the estimation of the TP (Gustine et al ; Décima et al ; Ohkouchi et al ). The β value presents relative initial differences between the δ 15 N Glu and δ 15 N Phe in primary producers (i.e., −8.4‰ for vascular C3 plants, +0.4‰ for C4 plants, +3.4‰ for algae, and + 2.6‰ for cyanobacteria) (Chikaraishi et al ; Chikaraishi et al ; Nielsen et al ).…”

Section: βCorr and The Contribution Of Vascular Plant As A Diet Resoumentioning

confidence: 99%

Elucidating food web structure of the Poyang Lake ecosystem using amino acid nitrogen isotopes and Bayesian mixing model

Zhang

Tian

Cao

et al. 2019

Limnology & Ocean Methods

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Compound‐specific isotope analysis of amino acids (CSIA‐AA) is regarded as a more advanced method of unraveling food web connections than the traditional bulk isotope approach. One of the most important assumptions of the CSIA‐AA approach is that the initial offset (β) between glutamate and phenylalanine in primary producers should remain unchanged. However, the considerable difference in β values between algae (+3.4‰) and vascular plants (−8.0‰) raises concern regarding the application of the CSIA‐AA approach for complex ecosystems that depend on both resources. In the present study, a Bayesian mixing model was used to estimate the individual contribution of basal dietary resources to each consumer of Poyang Lake, and then, the β was reevaluated to adapt to the assimilation of the individual primary producer for each consumer specimen. In general, the contributions of vascular plant‐derived resources to most consumers are consistent with their feeding behaviors. The smaller contribution of vascular plants to planktivorous fish (usually less than 20%) is biologically expected because of their feeding ecology. Using this strategy, we successfully obtained realistic trophic positions (TP) of consumers in Poyang Lake, which are significantly different from traditional TPalgae or TPvascular. For instance, the TP value of grass carp (2.04) was consistent with the feeding behavior of this fish, i.e., they primarily feed on vascular hydrophytes. Therefore, the combination of the CSIA‐AA and Bayesian mixing model provides a better understanding of food web structures, even in a complex freshwater ecosystem.

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“…The link between high winter δ 15 N ratios and catabolism of body stores, in particular maternal body proteins, suggests that high δ 15 N ratios in winter may be a suitable indicator of poor calf production. Such a relationship has previously been established for both reindeer and muskoxen using stable isotopes from excreta [ 12 , 28 , 29 , 60 , 62 ]. The results of the current study highlight the potential of using stable isotopes in hair to monitor muskox populations, if one can establish the link between the dietary signal in muskox guard hairs, and vital population demographic parameters such as calf recruitment.…”

Section: Discussionmentioning

confidence: 98%

Show Me Your Rump Hair and I Will Tell You What You Ate – The Dietary History of Muskoxen (Ovibos moschatus) Revealed by Sequential Stable Isotope Analysis of Guard Hairs

et al. 2016

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The nutritional state of animals is tightly linked to the ambient environment, and for northern ungulates the state strongly influences vital population demographics, such as pregnancy rates. Continuously growing tissues, such as hair, can be viewed as dietary records of animals over longer temporal scales. Using sequential data on nitrogen stable isotopes (δ15N) in muskox guard hairs from ten individuals in high arctic Northeast Greenland, we were able to reconstruct the dietary history of muskoxen over approximately 2.5 years with a high temporal resolution of app. 9 days. The dietary chronology included almost three full summer and winter periods. The diet showed strong intra- and inter-annual seasonality, and was significantly linked to changes in local environmental conditions (temperature and snow depth). The summer diets were highly similar across years, reflecting a graminoid-dominated diet. In contrast, winter diets were markedly different between years, a pattern apparently linked to snow conditions. Snow-rich winters had markedly higher δ15N values than snow-poor winters, indicating that muskoxen had limited access to forage, and relied more heavily on their body stores. Due to the close link between body stores and calf production in northern ungulates, the dietary winter signals could eventually serve as an indicator of calf production the following spring. Our study opens the field for further studies and longer chronologies to test such links. The method of sequential stable isotope analysis of guard hairs thus constitutes a promising candidate for population-level monitoring of animals in remote, arctic areas.

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Environmental and Physiological Influences to Isotopic Ratios of N and Protein Status in a Montane Ungulate in Winter

Cited by 8 publications

References 73 publications

Seasonal Variation in Stable Carbon and Nitrogen Isotope Values of Bats Reflect Environmental Baselines

Seasonal Variation in Stable Carbon and Nitrogen Isotope Values of Bats Reflect Environmental Baselines

Elucidating food web structure of the Poyang Lake ecosystem using amino acid nitrogen isotopes and Bayesian mixing model

Show Me Your Rump Hair and I Will Tell You What You Ate – The Dietary History of Muskoxen (Ovibos moschatus) Revealed by Sequential Stable Isotope Analysis of Guard Hairs

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