Effects of Pleistocene climates on local environments and dietary behavior of mammals in Florida

Abstract

Stable oxygen (δ18O) and carbon (δ13C) isotope values from fossil tooth enamel can be used to better understand mammalian responses to changing climates and impacts of increasing evaporative conditions on the diets of Pleistocene taxa. Previous work demonstrated dietary modification in response to interglacial warming; however, it is difficult to know if these changes resulted from changing climates, alterations of their habitat, or both. Here, we further investigate the influences of increasing evaporative conditions and changing vegetation on diets using oxygen and carbon isotopes from medium- to large-bodied herbivores from Pleistocene sites in Florida (Haile 8A, Tri-Britton, Leisey Shell Pit 1A, Inglis 1A). Bulk and serial stable isotope values indicate that Tri-Britton was the warmest and driest site with forests and C4 grasslands, and may have been able to support closely related taxa (e.g. multiple peccaries and camelids). In contrast to Tri-Briton and Leisey Shell Pit 1A, Haile 8A was the wettest site and may have represented a transitional climate. The diets of Hemiauchenia, Platygonus, and Mylohyus changed from browsing (Inglis 1A, Haile 8A) to mixed feeding (Leisey Shell Pit 1A, Tri-Britton), potentially in response to warmer temperatures and/or more arid environments. Mammut, Odocoileus, and Palaeolama maintained primarily C3 diets at all sites; however, δ13C values were greatest at Leisey Shell Pit 1A and Tri-Britton. Tapirus and Equus also had significantly greater δ13C values at Tri-Britton as compared to other sites, further suggesting more evaporative conditions. With higher temperatures and/or increased aridity, dietary generalists modified their diets more than specialists, often including a greater proportion of C4 vegetation than during cooler and/or wetter periods. Collectively, these data suggest that increased evaporative conditions during the Pleistocene may have contributed to a broader range of diets in generalist herbivores when compared to dietary specialists.