Supporting isotopic data for: Amino acid isotope analysis reveals variation in gut microbial contribution to host protein metabolism in a wild small mammal community

Herbivory is a dominant feeding strategy among animals, yet herbivores are
often protein limited. The gut microbiome is hypothesized to help maintain
host protein balance by provisioning essential macromolecules, but this
has never been tested in wild consumers. Using amino acid carbon (δ13C)
and nitrogen (δ15N) isotope analysis, we estimated the proportional
contributions of essential amino acids (AAESS) synthesized by gut microbes
to five co-occurring desert rodents representing herbivorous, omnivorous,
and insectivorous functional groups. We found that herbivorous rodents
occupying lower trophic positions (Dipodomys spp.) routed a substantial
proportion (~40–50%) of their AAESS from gut microbes, while higher
trophic level omnivores (Peromyscus spp.) and insectivores (Onychomys
arenicola) obtained most of their AAESS (~58%) from plant-based energy
channels but still received ~20% of their AAESS from gut microbes. These
findings empirically demonstrate that gut microbes play a key functional
role in host protein metabolism in wild animals.