Integrative isotopic Paleoecology (δ13C, δ18O) of a Late Pleistocene vertebrate community from Sergipe, NE Brazil

Isotopes are one of the best tools to reconstruct the Paleoecology of extinct taxa, yielding insights about their diet (through carbon; C3 and C4 plants), niche breadth (BA) and the environment in which they lived. In the present work we go deeper in the use of isotopes and explore a mathematical mixing model with the stable isotopes of two elements (carbon and oxygen) to (1) suggest the relative contribution of four types of food resources (leaves, fruits, roots and C4 grass) for meso- and megaherbivores (weight > 100 kg) that lived in the Late Pleistocene of Poço Redondo, Sergipe, Brasil, and (2) evaluate which of these herbivores could be the potential prey for the carnivores Smilodon populator and Caiman latirostris. To explore the intra/interspecific competition of these fauna, we generate weight estimation, standardized niche breadth (BA) for the meso-megamammals from Sergipe and compare with data from the meso-megaherbivores from Africa, concluding that Eremotherium laurillardi and Toxodon platensis were the best resource competitors in the Late Pleistocene of Sergipe, and reinforcing their importance as key species in this extinct community. Finally, we reconstructed the paleoenvironment in which the vertebrate community of Sergipe lived, estimating Mean Annual Temperature (°C), Mean Annual Precipitation, Biomass and Energy Expendidure, noting that environments in the Late Pleistocene of Sergipe were similar to those of Africa nowadays, but hotter and with more energy expenditure for these meso-megamammals.


Introduction
In order to complement our results, and refine the determination of the isotopic 147 diet of Sergipe taxa, we included previously published isotopic data (δ 13 C and δ 18 O, of 148 which most have 14 C AMS datings; Table S1) and 14 C AMS and ESR datings of E. To enhance discussion, we calculated the estimated weight (1) for megafauna 173 species that lived in Sergipe (Table 1, Table S1) (Table S2), through a circumference estimation: C = dπ. 186 Xenarthrans have flat femur with a high circumference of diaphysis values, 187 leading to an overestimation of weight if using standard method. To avoid this problem, 188 we multiplied their femur circumference by 0.4, trying to acquire a more realistic 189 weight estimation (2). The regression adaptation was calibrated using values for three  (Table S2). Exceptions were made for gliptodonts (Panochthus and 193 Glyptotherium) which weight were estimated by original regression proposed by (4), where n is total number of isotope bins available. Values lower or equal to 0.5 204 suggests a specialist, and above 0.5, a generalist.   weighting between 600 kg to 3,500 kg; and, finally, +15 ‰ for taxa weighting more 258 than 3,500 kg (Table S3).

259
Considering an enrichment of 12-15 ‰, δ 13 C values lower than -15 ‰ to -12 ‰ 260 are typical of animals with a diet consisting exclusively of C 3 plants, while δ 13 C values 261 higher than -1 ‰ to +2 ‰ are consistent with a diet based on C 4 plants. Unfortunately, we did not find any comparable estimation for this taxa. However, it is 360 similar to the weight of the extant armadillo Priodontes maximus (w = ~19-33 kg), and 361 much smaller than Holmesina paulacoutoi (w = 120 kg).

362
The weight of Glyptotherium sp. (w = 710 kg) was more similar to that suggested 363 for Glyptodon reticulatus (w = 862 kg) than to Glyptodon clavipes (w = 2,000 kg; Table   364 1 Attempting to understand better isotopic paleoecology of Sergipe Pleistocene 384 mammals taxa, we reunite here, to compare, available isotopic data for 11 extant 385 mammals from Africa (Table 3 and Figure 3A), to analyze the isotopic diet patterns  which have a diet composed mainly by C 4 grass (varying from 92 % to 100 %; Table 3; 404 Figure 3A-B), consumption of roots and leaves were low (p i = 0-6% and 1-4 %, 405 respectively), and fruits (p i = 0-1 %) virtually inexistent.

531
We know that C. latirostris could not actively hunt mammals taxa found in 532 Sergipe, as they weight more than 420 kg (Table 4) Table 3). Despite these high values, competition indexes 547 (Table 5) allow us to suggest that intraspecific competition (IC; Table 5) was higher 548 than interspecific competition with other grazers (SC ; Table 5), which was virtual 549 inexistent ( Figure 6), probably because they fed on different taxa of C 4 grass (e.g.

579
The mixed-feeder guild was composed of eight taxa, two megaherbivores (E.

583
As in Africa all mixed-feeders were better competitors than grazers, presenting 584 better IC (Table 5). The better competitors in the Late Pleistocene of Poço Redondo, E.