Isotopic Discrimination Factors (Δ13C and Δ15N) between Tissues and Diet of the Broad-Snouted Caiman (Caiman latirostris)

Marques, Thiago S.; Bassetti, Luís A. B.; Lara, Neliton R. F.; Araújo, Márcio S.; Piña, Carlos Ignácio; Camargo, Plínio Barbosa de; Verdade, Luciano Martins

doi:10.1670/12-274

Cited by 16 publications

(17 citation statements)

References 56 publications

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“…TDF of 15 N in crocodilians (around 1.0‰ 15 , 16 can be much lower than in most organisms studied (3.4‰ 4 , 6 ). Thus, we used a conservative Δ 15 N value of 2.5‰ for crocodilians which is a mean TDF value also reported elsewhere 61 .…”

Section: Methodsmentioning

confidence: 67%

“…Not all species show similar TDF values; those with diets high in protein show higher TDF values 11 , 59 . Independent of the diet, some species of crocodilians, show much lower discrimination values than other vertebrates 15 , 16 . This is crucial, because the importance of growth-related factors will be greater in relation to food-related factors for these species.…”

Section: Discussionmentioning

confidence: 97%

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Body size is more important than diet in determining stable-isotope estimates of trophic position in crocodilians

Villamarín

Jardine

Bunn

et al. 2018

Sci Rep

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The trophic position of a top predator, synonymous with food-chain length, is one of the most fundamental attributes of ecosystems. Stable isotope ratios of nitrogen (δ15N) have been used to estimate trophic position of organisms due to the predictable enrichment of 15N in consumer tissues relative to their diet. Previous studies in crocodilians have found upward ontogenetic shifts in their ‘trophic position’. However, such increases are not expected from what is known about crocodilian diets because ontogenetic shifts in diet relate to taxonomic categories of prey rather than shifts to prey from higher trophic levels. When we analysed dietary information from the literature on the four Amazonian crocodilians, ontogenetic shifts in dietary-based trophic position (TPdiet) were minimal, and differed from those estimated using δ15N data (TPSIA). Thus, ontogenetic shifts in TPSIA may result not only from dietary assimilation but also from trophic discrimination factors (TDF or Δ 15N) associated with body size. Using a unique TDF value to estimate trophic position of crocodilians of all sizes might obscure conclusions about ontogenetic shifts in trophic position. Our findings may change the way that researchers estimate trophic position of organisms that show orders of magnitude differences in size across their life span.

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Section: Methodsmentioning

confidence: 67%

Section: Discussionmentioning

confidence: 97%

Body size is more important than diet in determining stable-isotope estimates of trophic position in crocodilians

Villamarín

Jardine

Bunn

et al. 2018

Sci Rep

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“…Similar experimental studies focusing on TDFs in the past have also avoided mixed-effects models supposedly for the same reason as we state (e.g. [ 49 , 50 , 51 ]). Measurements of mean δ 13 C and δ 15 N values are reported as means ± SD.…”

Section: Methodsmentioning

confidence: 73%

Trophic Discrimination Factors of Stable Carbon and Nitrogen Isotopes in Hair of Corn Fed Wild Boar

et al. 2015

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Stable isotope measurements are increasingly being used to gain insights into the nutritional ecology of many wildlife species and their role in ecosystem structure and function. Such studies require estimations of trophic discrimination factors (i.e. differences in the isotopic ratio between the consumer and its diet). Although trophic discrimination factors are tissue- and species- specific, researchers often rely on generalized, and fixed trophic discrimination factors that have not been experimentally derived. In this experimental study, captive wild boar (Sus scrofa) were fed a controlled diet of corn (Zea mays), a popular and increasingly dominant food source for wild boar in the Czech Republic and elsewhere in Europe, and trophic discrimination factors for stable carbon (Δ13C) and nitrogen (Δ15N) isotopes were determined from hair samples. The mean Δ13C and Δ15N in wild boar hair were –2.3 ‰ and +3.5 ‰, respectively. Also, in order to facilitate future derivations of isotopic measurements along wild boar hair, we calculated the average hair growth rate to be 1.1 mm d-1. Our results serve as a baseline for interpreting isotopic patterns of free-ranging wild boar in current European agricultural landscapes. However, future research is needed in order to provide a broader understanding of the processes underlying the variation in trophic discrimination factors of carbon and nitrogen across of variety of diet types.

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“…Low TDFs have also been suggested for crocodilians (Marques et al., 2014) and could be common in large‐bodied ectothermic predators. However, it is unlikely that most of the prey taken by arapaima also have such low TDFs.…”

Section: Discussionmentioning

confidence: 84%

Uncertainties associated with trophic discrimination factor and body size complicate calculation of δ¹⁵N‐derived trophic positions in Arapaima sp.

Jacobi

Villamarı́n

Jardine

et al. 2020

Ecology of Freshwater Fish

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Stable isotope ratios of nitrogen (δ15N) have been used to estimate trophic position (TP) of organisms due to the predictable enrichment of nitrogen‐15 in consumer tissues relative to their diet. We explored estimates of trophic position using liver and muscle δ15N and stomach content analysis in a broad size range of Arapaima sp. from Amazonian floodplain lakes. Estimates of TP based on liver δ15N were more closely related to the stomach content data than estimates based on muscle δ15N, possibly because of the higher turnover of nitrogen in liver. Total length and season explained most of the variation in TP values estimated from δ15N, showing that they have more effect than prey trophic position on δ15N values. The TP estimated by identification of stomach content was 3.6 and was unrelated to the size of the arapaima. This highlights the need for a better understanding of the factors that affect values of δ15N and stomach content analysis is still needed to unravel the trophic ecology of predatory fishes.

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Isotopic Discrimination Factors (Δ¹³C and Δ¹⁵N) between Tissues and Diet of the Broad-Snouted Caiman (Caiman latirostris)

Cited by 16 publications

References 56 publications

Body size is more important than diet in determining stable-isotope estimates of trophic position in crocodilians

Body size is more important than diet in determining stable-isotope estimates of trophic position in crocodilians

Trophic Discrimination Factors of Stable Carbon and Nitrogen Isotopes in Hair of Corn Fed Wild Boar

Uncertainties associated with trophic discrimination factor and body size complicate calculation of δ¹⁵N‐derived trophic positions in Arapaima sp.

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Isotopic Discrimination Factors (Δ13C and Δ15N) between Tissues and Diet of the Broad-Snouted Caiman (Caiman latirostris)

Cited by 16 publications

References 56 publications

Body size is more important than diet in determining stable-isotope estimates of trophic position in crocodilians

Body size is more important than diet in determining stable-isotope estimates of trophic position in crocodilians

Trophic Discrimination Factors of Stable Carbon and Nitrogen Isotopes in Hair of Corn Fed Wild Boar

Uncertainties associated with trophic discrimination factor and body size complicate calculation of δ15N‐derived trophic positions in Arapaima sp.

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Isotopic Discrimination Factors (Δ¹³C and Δ¹⁵N) between Tissues and Diet of the Broad-Snouted Caiman (Caiman latirostris)

Uncertainties associated with trophic discrimination factor and body size complicate calculation of δ¹⁵N‐derived trophic positions in Arapaima sp.