THE EFFECT OF CLIMATE CHANGE AND BIODIVERSITY LOSS ON NEOTOMA SPP. FROM ~20,000 CAL BP TO PRESENT

Changing climate and the loss of 80% of large-bodied herbivores at the terminal Pleistocene led to substantial restructuring of North American ecosystems, which likely had important impacts on the species that survived the extinction event. Here we focus on the effects of these events on the ecology and physiology of Neotoma (woodrat) using the finely resolved temporal record from Hall’s Cave in the Edwards Plateau, Texas. We characterize changes in body size and diet over the past ~20,000 years using fossil teeth measurements (n=396) and bone collagen (n=285) carbon (δ¹³C) and nitrogen (δ¹⁵N) isotope values. We found Neotoma to be highly sensitive to climatic changes over time. Maximum body size in Neotoma significantly decreased with increasing temperatures during the Holocene, in agreement with past studies that found members of this genus adhere to Bergmann’s Rule. Changes in δ¹³C and δ¹⁵N isotopic niche space indicate a shift from a C₃-based diet in the Pleistocene to a more mixed C₃-C₄/CAM diet during the Holocene, associated with known landscape shifts from more mesic to xeric conditions and associated vegetation communities across time. The combined decrease in body size and dietary changes may also indicate a species turnover for the genus Neotoma in the region, specifically a transition from the initially abundant Neotoma floridana, which is generally associated with more deciduous environments, to N. micropus, which today is common in arid and semi-arid environments. We estimate the species shift occurred at approximately 7,000 cal BP.