Reconstruções paleoecológicas da megafauna do Pleistoceno final da Região Intertropical Brasileira

Abstract

Pleistocene megafauna, composed of large-bodied mammals resilient to Quaternary climatic fluctuations, exhibited a wide distribution across the Brazilian territory, particularly within the Brazilian Intertropical Region, favored by high climatic suitability. The subsequent weakening of these populations, driven by climate changes and associated factors such as the arrival of PaleoIndians in South America, contributed to their extinction at the beginning of the Holocene, resulting in profound changes in ecosystem structure and functioning. The ecology of extinct species can be investigated through paleoecological tools, including stable and radiogenic isotope analyses. Stable carbon (δ¹³C) and oxygen (δ¹⁸O) isotopes allow inferences regarding diet and paleoenvironments, whereas radiogenic isotopes, such as strontium (⁸⁷Sr/⁸⁶Sr), enable the reconstruction of mobility and migration patterns. In tropical and subtropical regions, these signals are preferentially obtained from bioapatite due to the frequent degradation of collagen. However, to ensure the reliability of isotopic results, it is essential to assess fossil preservation and the potential influence of diagenetic processes, which remain poorly investigated in South America. In this study, we aimed to generate robust paleoecological inferences for different Pleistocene megafaunal species across distinct environmental contexts and analytical approaches. In the first chapter, we evaluated the quality of bioapatite in samples of Eremotherium laurillardi and Toxodontinae by comparing enamel, dentine, and associated soil, as well as testing sampling strategies for fossils recovered from natural tank deposits. In the second chapter, serial isotopic analyses were applied to identify seasonal dietary patterns in these species. In the third chapter, strontium isotope analyses demonstrated that Notiomastodon platensis exhibited migratory behavior, being capable of crossing geographic barriers such as the São Francisco River, and allowed the identification of the most recent specimen published to date. Finally, in the fourth chapter, we integrate isotopic data, climatic suitability, morphological attributes, and characteristics of fruits potentially consumed by browsing species, revealing a significant negative association between mean seed diameter and herbivore body mass. Taken together, this thesis strengthens methodological protocols, expands the application of isotopes in tropical contexts, and presents novel results on diet, seasonality, migration, and ecological interactions of Pleistocene megafauna in Brazil.