Info: Zenodo’s user support line is staffed on regular business days between Dec 23 and Jan 5. Response times may be slightly longer than normal.

Dryad
Published July 6, 2023 | Version v1
Software Open

Meta-analysis and critical review of trophic discrimination factors (Δ13C and Δ15N): importance of tissue, trophic level, and diet source

Creators

  • 1. East Tennessee State University
  • 2. Stony Brook University
  • 3. University of New Hampshire

Description

  1. Robustly quantifying dietary resource use and trophic position using stable isotopes requires accurate trophic discrimination factors (TDF; Δ13C and Δ15N for carbon and nitrogen, respectively), defined as the isotopic difference between consumer and diet. Early TDF studies converged on values of around 1.0‰ for Δ13C and 3.4‰ for Δ15N, but more recent work indicates that TDF values may be more nuanced, depending on taxa, tissues, trophic level, and diets. Yet, the relative importance of these factors remains unclear.
  2. Focusing on vertebrates (birds, fish, herptiles, and mammals), we conducted a literature review of 279 studies that estimated TDF values and used a Bayesian framework to determine how tissue type, trophic level, and diet source influence variation in Δ13C and Δ15N. Additionally, we reviewed 358 trophic ecology studies to determine if studies accounted for these factors during their TDF selection process.
  3. For Δ13C, vertebrates showed consistent patterns among tissue types (likely influenced by amino acid composition) and between trophic levels and diet sources (likely a result of dietary protein content and metabolic routing). Comparatively, for Δ15N, vertebrates showed considerable variation among tissue types and trophic levels, likely due to differences in tissue synthesis and physiological capabilities. Overall, Δ13C ranged from -5.1‰ to 9.1‰ and Δ15N from -3.3‰ to 9.7‰, underscoring that 1.0‰ for Δ13C and 3.4‰ for Δ15N are not universally appropriate. Moreover, both Δ13C and Δ15N varied by more than 9‰ within a single species and tissue type, demonstrating that using TDF values from the same, or similar, species may not be appropriate if diet and trophic level are not considered.
  4. Despite the importance of diet source on TDF values, most trophic ecology studies did not account for it. Further, most fish studies relied on literature review values that failed to account for tissue type, trophic level, and diet source. To aid ecologists in diet and trophic assessments of vertebrates, we used our meta-analysis to model taxon-specific TDF estimates (mean ± SD) for each tissue type, trophic level, and diet source combination. These more refined TDF values should improve ecological assessments that use stable isotopes.

Files

Files (195.1 kB)

Name Size Download all
md5:13b21df2f23c62c1a93e89c24b11d84b
5.1 kB Download
md5:bfbd8f7d42cb6be4fdbfbc9b6293ee77
10.9 kB Download
md5:84b952059e2eb0714a0dbd9c92cff683
16.7 kB Download
md5:337eec198a4c1e8791ff9bd41cff5cb9
5.7 kB Download
md5:e09b1083ad10763478d636e661faced8
8.0 kB Download
md5:7b021b2a2c63f0576570262dfbdb4e03
26.7 kB Download
md5:7897d6803a7a5c1af573783f4711e8b3
30.5 kB Download
md5:9a50db9344435baa6cdd7f70c1343146
5.5 kB Download
md5:a0d3948eaf7f0bc5f4a886a55331d0d8
86.0 kB Download

Additional details

Related works

Is source of
10.5061/dryad.z08kprrjk (DOI)