Kessler, Camille Pauline

Since the mid-Pleistocene, evolutionary histories of North American species were shaped by extreme climatic oscillations involving major range and habitat shifts at a rapid pace. The peopling of the continent and the subsequent human colonisation waves created further pressures affecting North American faunal and plant populations. Cervidae (deer family) are a diverse group which arrived in North America approximately 5 million years ago, and is represented on the continent by several extant species. The overarching aim of my thesis is to understand how North America's dynamic history shaped the evolutionary trajectory of the region's Cervidae species. In Chapter 2, I investigated the speciation and hybridisation history of the sister species white-tailed (Odocoileus virginianus) and mule deer (Odocoileus hemionus) using whole genome data of individuals from across their ranges, including zones of sympatry and allopatry. I found negligible patterns of ancient gene-flow suggesting white-tailed and mule deer divergence occurred via drift and their hybridisation is the result of secondary contact. In Chapter 3, I furthered our understanding of the Odocoileus species pair evolutionary history through explicit demographic inference and selection analyses. I used deer samples from across North America and found strong signals of climate- and human-induced population declines. Particularly, this work highlights the impact of European settlers and patterns of conservation concerns for mule deer. For Chapter 4, I clarified the phylogenetic relationship of a contentious taxon, Torontoceros hypogaeus, that went extinct during the late Pleistocene extinction event. I analysed 11k years old DNA of the single specimen representing the species, performed phylogenetic and divergence analyses, and found it belongs to the Odocoileus genus as Odocoileus (Torontoceros) hypogaeus which should be included in North America's late Pleistocene extinction list. Finally, in Chapter 5, I investigated genetic diversity over time in five North American Cervidae using contemporary and ancient DNA. I found patterns of change in genetic diversity that are consistent with known dispersal and demographic histories of our target species. Altogether, my thesis provides valuable insight into the evolutionary history of Northern American Cervidae, and on how they have been impacted by the continent's dynamic past.

Author Keywords: Cervidae, Demographic history, Extinction, Human impact, Hybridisation, Speciation genomics