Supporting Data for: Assessing the potential of amino acid δ13C and δ15N analysis in terrestrial and freshwater ecosystems

Understanding the structure and dynamics of food webs requires accurate estimates of energy flow among organisms. Bulk tissue carbon (δ13C) and nitrogen (δ15N) isotope analysis is often used to this end, however, the limitations of this technique can outweigh the benefits. The isotope analysis of individual amino acids is being increasingly employed to trace energy flow and estimate consumer trophic level. Central to this compound-specific approach are the concepts of essential amino acid (AAESS) δ13C fingerprinting and amino acid (AA) δ15N beta-values, both of which have been understudied and are poorly constrained in terrestrial and freshwater producers.
We present AAESS δ13C data for 112 terrestrial and freshwater producers collected from two aridland habitats in the northern Chihuahuan Desert (New Mexico, USA) and AA δ15N data for a subset (n=28) of these samples. We characterized AAESS δ13C fingerprints by performing linear discriminant analysis on the δ13C values of isoleucine, le...