Geographic variability of carbon and nitrogen isotope ratios of nonvolant terrestrial small mammals (Rodentia) across 3 Brazilian biomes.

This study investigates the spatial variability of stable carbon (δ¹³C) and nitrogen (δ¹⁵N) isotopic compositions in nonvolant small mammals (order Rodentia) across Brazil's three main biomes: Amazon, Atlantic Forest, and Cerrado. Using isotopic data from 804 specimens, the research demonstrates that isotopic signatures in these mammals reflect the distribution of C3 and C4 plants, with terrestrial mammals in the Cerrado showing higher δ¹³C values consistent with greater C4 plant consumption, while arboreal mammals exhibit less pronounced biome differences. Bayesian mixing models estimate dietary contributions from C3 plants, C4 plants, and arthropods, revealing that C3 plants dominate diets overall but C4 plant intake increases from Amazon to Cerrado and is higher in terrestrial and scansorial mammals than arboreal ones. The study also develops isoscapes and sourcescapes to map isotopic and dietary source variability, highlighting how landscape alteration—particularly replacement of native vegetation with C4 crops—may influence small mammal feeding ecology and trophic structures in these biodiverse regions.