Meta‐analysis of primary producer amino acid δ ¹⁵ N values and their influence on trophic position estimation

Compound-specific stable isotope analysis of individual amino acids (CSIA-AA) has emerged as a transformative approach to estimate consumer trophic positions (TPCSIA) that are internally indexed primary producer nitrogen baselines. Central accurate TPCSIA estimation is an understanding beta (β) values—the differences between and source AA δ15N values in the producers at base consumers’ food web. Growing evidence suggests higher taxonomic tissue-specific β value variability than typically appreciated. This meta-analysis fulfils pressing need comprehensively evaluate relevant sources its contribution uncertainty. We first synthesized all published data investigate ecologically (e.g. taxonomy, tissue type, habitat mode photosynthesis). then reviewed biogeochemical mechanisms underpinning variability. Lastly, we evaluated sensitivity estimates uncertainty mean βGlx-Phe Glx-Phe discrimination factors (TDFGlx-Phe). show variation two times greater previously considered, with degree vascularization, not type (terrestrial vs. aquatic), providing greatest (vascular autotroph = −6.6 ± 3.4‰; non-vascular +3.3 1.8‰). Within vascular plants, secondarily contributed variability, but found no clear distinction among C3, C4 CAM plant values. Notably, βGlx-Lys (+2.5 1.6‰) considerably less variable values, making Lys useful tracer production terrestrial systems. Our multi-trophic level analyses demonstrate highly sensitive changes both TDFGlx-Phe relative influence dissipates levels. results highlight integral position estimation. outline four key recommendations for identifying, constraining accounting improve accuracy precision moving forward. must ultimately expand libraries better understand mechanistic drivers variation.