Western University Scholarship@Western Electronic Thesis and Dissertation Repository 10-27-2016 12:00 AM Giant Beaver (Castoroides) Palaeoecology Inferred from Stable Isotopes Tessa Plint The University of Western Ontario Supervisor Fred J. Longstaffe The University of Western Ontario Graduate Program in Geology A thesis submitted in partial fulfillment of the equirr ements for the degree in Master of Science © Tessa Plint 2016 Follow this and additional works at: https://ir.lib.uwo.ca/etd Part of the Biogeochemistry Commons, Paleobiology Commons, and the Paleontology Commons Recommended Citation Plint, Tessa, "Giant Beaver (Castoroides) Palaeoecology Inferred from Stable Isotopes" (2016). Electronic Thesis and Dissertation Repository. 4236. https://ir.lib.uwo.ca/etd/4236 This Dissertation/Thesis is brought to you for free and open access by Scholarship@Western. It has been accepted for inclusion in Electronic Thesis and Dissertation Repository by an authorized administrator of Scholarship@Western. For more information, please contact [email protected]. Abstract Stable isotope analysis was used to explore unresolved questions about the palaeoecology of the extinct Pleistocene giant beaver (Castoroides). The 13C, δ15N, and 18O of bone collagen and structural carbonate from enamel served as proxies for palaeodiet and palaeoclimate. A new baseline for freshwater and terrestrial plant 13C and δ15N was utilized in a mixing model (SIAR) to assess rodent feeding niche. SIAR analysis indicated that Castoroides’ consumed a diet of predominantly macrophytes, making them reliant on wetland habitat for food. Based on isotopic data for potential modern analog species (Castor and Ondatra), SIAR also indicated that Castor and Castoroides occupied complementary dietary niches, allowing them to share habitat space throughout the Pleistocene. The 13C and 18O of Castoroides’ ever-growing incisors also recorded seasonal fluctuations in diet and climate. Wetland loss due to climate change during the Last Glacial Maximum, and increased competition for habitat, probably factored into Castoroides’ extinction. Keywords Castoroides, Stable Isotope, Pleistocene, Palaeodiet, Palaeoecology, Megafauna, North America i Acknowledgments I would like to thank the following people, without whom the completion of this thesis would not have been possible: Fred and Lisa, for the research opportunities and support you have both provided. Rachel Schwartz-Narbonne, for being an excellent (de)mentor. My parents, for their continual support and encouragement (and chocolate). Michael Burzynski, Michelle Viglianti, Farnoush Tahmesabi, Racel Sopoco, Natalia Rybczynski, and Grant Zazula, for your individual support and help during the research process. Kim, Li, and Grace for all of your patience and help in the lab! Office 1031 for being my on-campus family, and the Junction crew for providing much needed sanity-time outside of academia. I would like to thank the following institutions and individuals who provide me with sample material: The Museum of the North, the Florida Museum of Natural History, the Canadian Museum of Nature, the Ohio Historical Society, the Vuntut Gwitchin First Nation Government, the Yukon Trappers Association, the Long Point Conservation Authority, the Wildlife Energetics and Ecology Lab at McGill University, Natasha Bumstead, Tom Porawski, and Bill Fitzgerald. This research was supported by funding from the following organizations: The Faculty of Science (University of Western Ontario), Alexander Graham Bell Canada Graduate Scholarship-Master’s, Northern Training Grant from the Northern Scientific Training Program, the Arcangelo Rea Family Foundation. L.S.I.S. is also supported through The Canada Foundation for Innovation, the Ontario Research Fund, and Natural Sciences and Engineering Research Tools and Infrastructure grants to F. J. Longstaffe. ii Table of Contents Abstract ................................................................................................................................ i Acknowledgments............................................................................................................... ii Table of Contents ............................................................................................................... iii List of Tables ................................................................................................................... viii List of Figures .................................................................................................................... ix Preface................................................................................................................................ xi Chapter 1 Introduction ........................................................................................................ 1 Introduction and Overview ..................................................................................... 1 Thesis Aim .............................................................................................................. 1 1.2.1 Research Questions ..................................................................................... 2 1.2.2 Proposed Modern Analogs .......................................................................... 2 Stable Isotopes in Palaeoecology ............................................................................ 3 1.3.1 Stable Carbon and Nitrogen Isotopes ......................................................... 5 1.3.2 Oxygen Isotopes.......................................................................................... 6 Research Design...................................................................................................... 7 Research Implications ............................................................................................. 8 Background Information ......................................................................................... 8 1.6.1 Setting: The late Pleistocene World ............................................................ 9 1.6.2 Dietary Baseline: Freshwater Macrophyte Biology .................................. 10 1.6.3 Castor canadensis: Ecological Summary ................................................. 14 1.6.4 Ondatra zibethicus: Ecological Summary ................................................ 16 1.6.5 Castoroides: Palaeontological Summary .................................................. 18 Sample Material .................................................................................................... 21 iii 1.7.1 Calcified Tissues - Bone ........................................................................... 21 1.7.2 Calcified Tissues - Teeth .......................................................................... 22 1.7.2.1 Rodent Dental Morphology ........................................................ 23 Organization of Dissertation ................................................................................. 25 References ............................................................................................................. 25 Chapter 2 Methodological Studies .................................................................................... 35 Introduction ........................................................................................................... 35 13 15 The effects of different defleshing practices on C and δ N of bulk collagen from modern mammalian bone ............................................................................. 35 2.2.1 Research Aim ............................................................................................ 35 2.2.2 Methodology ............................................................................................. 36 2.2.3 Results ....................................................................................................... 39 2.2.4 Discussion ................................................................................................. 41 2.2.5 Conclusions ............................................................................................... 42 13 18 The effects of sample pretreatment on δ C and δ O of structural carbonates from enamel bioapatite .................................................................................................. 43 2.3.1 Overview and Research Aim .................................................................... 43 2.3.2 Methodology ............................................................................................. 49 2.3.2.1 Sampling Strategy ...................................................................... 49 2.3.2.2 FTIR Methodology ..................................................................... 49 2.3.2.3 Pretreatment Methodology ......................................................... 50 2.3.3 Results ....................................................................................................... 51 13 18 2.3.3.1 Enamel Csc and Osc ............................................................ 51 2.3.3.2 FTIR Parameters ......................................................................... 52 2.3.4 Discussion ................................................................................................. 53 2.3.5 Conclusions ............................................................................................... 55 References ............................................................................................................. 56 iv Chapter 3 Isotopic