Isotopic paleoecology (δ13C, δ18O) of Late Quaternary megafauna from Mato Grosso do Sul and Bahia States, Brazil

In the present study, the paleoecology (diet and niche width) of Late Quaternary megamammals that inhabited the Brazilian Intertropical Region (BIR) was assessed at two sites in the states of Bahia and Mato Grosso do Sul. The δ¹³C analyses suggest a generalist diet for Notiomastodon platensis, Palaeolama major, Holmesina paulacoutoi and Glyptotherium sp., while Equus neogeus was a grazer with a diet consisting exclusively of C₄ grasses, and Eremotherium laurillard, a predominant browser with a diet consisting predominantly of C₃ plants. A distinct diet pattern was inferred for one species: Toxodon platensis with a mixed-diet preferring C₄ grasses in Mato Grosso do Sul but predominantly the C₃ feeder in Bahia. These results show a high ecological plasticity of this species and may suggest distinct ecological pressures or different vegetation configurations in the two regions. Diet reconstitutions based on δ¹³C analyses suggest that an open savanna-like landscape predominated in both areas. The δ¹⁸O values reveal that Mato Grosso do Sul could have experienced wetter climatic conditions than Bahia during the Late Quaternary, suggesting a humid corridor in midwestern Brazil, or that there were different contents of δ¹⁸O of water sources between these areas. Hence, we assume that the same faunistic composition in different geographical areas is not enough to delimit the ecosystems of the BIR, and we recommend that the definitions of BIR should be revised to include more refined paleoclimate data. Other studies around the world should consider the same for delimitations of zoogeographic regions.