Reevaluating trophic discrimination factors ( Δδ 13 C and Δδ 15 N ) for diet reconstruction

作者：Ryan B. Stephens, Andrew P. Ouimette, Erik A. Hobbie, Rebecca J. Rowe · 发表于：Ecological Monographs · 年份：2022 · DOI：10.1002/ecm.1525 · 被引用次数：64 · 研究领域：Isotope Analysis in Ecology、Marine animal studies overview、Mercury impact and mitigation studies

Abstract Stable isotope analysis is increasingly being used to assess diet and trophic positions of animals. Such assessments require estimates of trophic discrimination factors (TDFs)—offset between the isotopic composition of diet and animal tissues—with imprecise applications of TDFs leading to biased conclusions in resource use. Because TDFs are unavailable for most species, ecologists often apply values from taxonomically similar species or use trophic step increases of approximately 1‰ for carbon (TDF‐δ 13 C) and 3‰ for nitrogen (TDF‐δ 15 N). Such practices may yield inaccuracies since TDFs vary greatly, even within a species. To better understand the factors that influence TDFs, we conducted a meta‐analysis of TDF‐δ 13 C and TDF‐δ 15 N for mammals and quantified variation in relation to consumer type (herbivore, omnivore, carnivore) and diet source (C 3 ‐based, C 4 ‐based, marine‐based, mixture). Additionally, to guide TDF choice, we used an isotopic data set of small mammal tissues and diet items to assess how predicted dietary contributions vary with TDFs estimated using (1) taxonomic relatedness, (2) consumer type and diet source, or (3) values derived from wild animals eating natural diets. Our meta‐analysis revealed that metabolic routing and interactions between consumer class, dietary source, and the protein versus energy content of diets best explained variation in TDF‐δ 13 C values (−1.5‰ to 7.3‰), whereas consumer class best explained variation in TDF‐δ 15 N ...