Abstract
This study aims at assessing resource and habitat use, niche occupation and trophic interactions from a stable isotope perspective on fossil mammals from the Argentine Pampas during the Great American Biotic Interchange (GABI). We present stable isotope data of more than 400 samples belonging to 10 mammalian orders and spanning a temporal range from ~9.5 Ma to ~12 ky. Rodents, notoungulates and pilosians record an increase in the consumption of C4 plants, whereas litopterns and cingulates show δ13C values that remain mostly within a C3-dominated diet. Our stable isotope data indicates that the expansion of C4 vegetation opened up new niche opportunities, probably alleviating resource competition among endemic taxa. Gomphothere, equid and camelid δ13C records show a broad variability pointing to consumption of C3 and mixed C3-C4 vegetation. This flexible dietary behavior may have facilitated the successful settlement of immigrant groups in South America. In the case of carnivorous taxa, Late Miocene pre-GABI endemic sparassodonts consumed prey from C3 environments, whereas immigrant carnivorans preferred prey from mixed C3-C4 areas. Our research contributes to the study of the GABI from a different perspective as stable isotope records permit to characterize, from a (semi)quantitative standpoint, ecological traits within extinct fauna.
Highlights
Understanding the evolution of mammalian communities throughout the history of Earth, their resource and habitat use, niche occupation and trophic relationships play fundamental roles as these variables determine interaction among species, which trigger profound changes in community structure leading to modern faunal structure[1]
Through the investigation of stable isotope data on a complete and updated record of Late Miocene to Late Pleistocene fossil mammals from Argentina, we aim at assessing whether (i) mammalian resource and habitat use and niche occupation changed throughout the Great American Biotic Interchange (GABI) time span; and (ii) the successful radiation of northern immigrants in South America was related to dietary behavior and habitat use, which might have provided a competitive advantage relative to southern residents
The Argentine Pampas (Buenos Aires and La Pampa provinces) have proven to be one of the best research areas to study the GABI from the perspective of the South American fossil record on account of its elevated number of Late Cenozoic fossil sites with diverse and abundant vertebrate faunal remains
Summary
Understanding the evolution of mammalian communities throughout the history of Earth, their resource and habitat use, niche occupation and trophic relationships play fundamental roles as these variables determine interaction among species, which trigger profound changes in community structure leading to modern faunal structure[1]. While there is a good chronology of the GABI pulses, little is known about the resource and habitat use, niche occupation and trophic interactions in South America related to this event or the extent to which the arrival of northern mammals affected ecological attributes. In this sense, previous stable isotope studies on vertebrate taxa have greatly contributed to unveil these questions[10,11,12,13,14,15,16,17]. Through the investigation of stable isotope data on a complete and updated record of Late Miocene to Late Pleistocene fossil mammals from Argentina, we aim at assessing whether (i) mammalian resource and habitat use and niche occupation changed throughout the GABI time span; and (ii) the successful radiation of northern immigrants in South America was related to dietary behavior and habitat use (in particular, niche breadth), which might have provided a competitive advantage relative to southern residents
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