Diversity dynamics and ecology of small mammals in relation to the Neogene tectonic and climate history of western North America by Tara Magnolia Smiley A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy (Geology) in the University of Michigan 2016 Doctoral Committee: Associate Professor Catherine Badgley, Chair Professor Daniel C. Fisher Associate Professor Nathan A. Niemi Assistant Professor Daniel L. Rabosky Associate Professor Nathan D. Sheldon © Tara M. Smiley 2016 DEDICATION To Tom Kunas for leading me to my first fossil & revealing the beauty in science ii ACKNOWLEDGMENTS The National Science Foundation Graduate Research Fellowship Program, the University of Michigan Rackham Predoctoral Fellowship and the Earth and Environmental Sciences Department supported this research. Funding from the Society of Vertebrate Paleontology Patterson Award, the Earth and Environmental Sciences Turner Award, the Inter-university Training for Continental-scale Ecology Research-in-Residence Award, and the Rackham Graduate School made fieldwork and laboratory analyses possible. I would like to acknowledge my collaborators and co-authors, without whom this research would not have been possible. I thank Jennifer Cotton and Ethan Hyland for assistance in the field, during sample analysis, and in manuscript preparation. Great appreciation goes to Bob Reynolds for introducing me to my field area and providing boundless enthusiasm and guidance in all things Mojave related. Thank you to Thure Cerling for teaching me so much about stable isotopes and supporting my research at the University of Utah. Several undergraduate students have helped with this research; in particular, Molly Moroz and Laura McQuarter have contributed greatly to data collection of modern and fossil heteromyids. I would also like to thank my dissertation committee members: Dan Fisher, Nathan Niemi, Dan Rabosky, and Nathan Sheldon. Their input throughout my graduate studies improved the research presented in this dissertation, pushed me to explore new and challenging concepts, and expanded my scientific scope. I would especially like to thank my advisor and chair, Catherine Badgley. Catherine’s wealth of knowledge, intellectual curiousity, devotion to thoughtful and well-constructed science, and passion for teaching, outreach, and conservation iii has inspired me from day one and will continue to influence me positively for the rest of my career. She has always been available to guide and support me through any task, and has done so with much warmth, encouragement, and a strong push when needed. Thank you, Catherine, for helping me to develop into the scientist I am today. Thank you to my fellow graduate students and the folks at the Museum of Paleontology, in particular Miriam Zelditch. I would especially like to thank the members of the Badgley Lab over the years, Rachel Cable, Mairin Balisi, Soledad Domingo, Katharine Loughney, and Jeff Shi for their company, assistant, and support from the office to the field. I would also like to thank my writing group, Susan Cheng, Lauren Cline, and Alison Gould for endless encouragement. Thank you to my friends in the Geology Department, especially Carli Arendt, Clay Tabor, Petr Yakovlev, Meghan Taylor, and Rich Fiorella for making my time here so enjoyable. A warm thanks goes to my friends outside of Michigan, Tiffany Blair, Amy Groesbeck, Lindsay Wahlborg, Manuela Molzan, and in particular Mama Hawa, Hawa, and Muku for helping me maintain an important sense of perspective throughout this journey. I would also like to express my graditude to my family. Thank you to my Mom for inspiring me to be adventurous and always optimistic. Thank you to my Dad for fueling my curiosity from a young age and challenging me to always ask more questions. I thank both of my parents for instilling in me a deep love of the natural world and my brother, Sam, for making grand outdoor adventures happen today. Thank you to my Grandma Judy for being my support here in Michigan. I am also appreciative of the love and encouragement I have received from Maria, Greg, Kurt, and Gretchen throughout my education. Finally, I am extraordinarily grateful to Pascal Title. Merci beaucoup for your constant love, support, patience, and encouragement – you have enriched my life in countless ways. iv TABLE OF CONTENTS DEDICATION .............................................................................................................................. ii ACKNOWLEDGMENTS ........................................................................................................... iii LIST OF FIGURES ..................................................................................................................... vi LIST OF TABLES ....................................................................................................................... ix ABSTRACT ................................................................................................................................... x CHAPTER 1 Introduction ............................................................................................................. 1 CHAPTER 2 Small-mammal isotope ecology tracks climate and vegetation gradients across western North America ......................................................................................... 21 CHAPTER 3 Evidence for early C4 grasses, habitat drying, and faunal response during the Miocene Climatic Optimum in the Mojave Region .............................................. 61 CHAPTER 4 Ecological response to environmental change: insights from the Miocene small- mammal record ................................................................................................... 111 CHAPTER 5 Detecting diversification processes in relation to tectonic history from an incomplete fossil record ...................................................................................... 163 CHAPTER 6 Conclusion........................................................................................................... 213 v LIST OF FIGURES Figure 1.1 Species richness of extant rodents in North America ..................................................17 Figure 1.2 Conceptual figure of landscape and climate factors influencing species diversity .....18 Figure 1.3 Neogene tectonic, climatic, and landscape events in western North America ............19 Figure 1.4 Rodent fossil diversity in the Great Basin over the Neogene ......................................20 Figure 2.1 Geographic ranges of Dipodomys ordii and Perognathus parvus and location of modern sampling sites ..................................................................................................45 Figure 2.2 Carbon, nitrogen, oxygen, and hydrogen isotopic compositions of modern heteromyid samples .........................................................................................................................46 Figure 2.3 Geographic variation in carbon isotopic composition (isoscape) of modern heteromyid diets and predicted C4 grass abundance in western North America .........47 Figure 2.4 Oxygen and hydrogen isotopic composition of Dipodomys ordii compared to global and local meteoric water lines ......................................................................................48 Figure S2.1 Representative climate gradients in western North America ....................................50 Figure 3.1 Geographic location and field photos of the Crowder and Cajon Valley formations, southern California .......................................................................................................95 Figure 3.2 Measured stratigraphic section, biostratigraphic ranges of mammalian faunas, and diversity in the Crowder Formation .............................................................................96 Figure 3.3 Measured stratigraphic sections (CV-SE and CV-NW), biostratigraphic ranges of mammalian faunas, and diversity in the Cajon Valley Formation ...............................97 Figure 3.4 Paleoenvironmental reconstruction of the Crowder Formation during the MCO .......98 Figure 3.5 Paleoenvironmental reconstructions of the CV-SE and CV-NW sections of the Cajon Valley Formation during the MCO ..............................................................................99 Figure 4.1 Geographic location of the Crowder and Cajon Valley formations in the vicinity of Cajon Pass, southern California .................................................................................149 vi Figure 4.2 Variation in isotopic composition and dental metrics of rodent assemblages from 17– 15 Ma in the Crowder Formation ...............................................................................150 Figure 4.3 Variation in isotopic composition and dental metrics of rodent assemblages from 16.5–13.7 Ma in the Cajon Valley Formation ...........................................................151 13 18 Figure 4.4 δ Cen and δ Oen values of rodent genera from Crowder and Cajon Valley assemblages ................................................................................................................152 13 Figure 4.5 Interspecific variation in δ Cdiet values for Crowder and Cajon Valley fossil assemblages compared to co-occurring heteromyid species in present-day communities ...............................................................................................................153 13 18 Figure S4.1 δ Cen and δ Oen values of individual