The Effects of Pleistocene Climatic Cycles on African Mammal Evolution: The Case of Hippotragin Antelopes

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Pleistocene climatic cycles produced glacial-interglacial climates at high latitudes and humid-arid cycles at low latitudes. Such low-latitude cyclic shifts on the order of 100,000 years in Africa are becoming clearer through geological and palynological studies, and their effects have been indirectly inferred through phylogeographic work on African herbivore species. We here propose to use population size histories through whole genome sequencing to test the magnitude of Pleistocene humid-arid cycling on the expansion and contraction of large mammal distributions in Africa. The taxon of focus is the Hippotragini, a clade with 8 historically extant species that span desert to savannah biomes. We will test the hypothesis that the arid-adapted species (Oryx + Addax) experienced maximal population sizes during arid phases (peak glacials). The inverse prediction is made for the more water-dependent taxa (Hippotragus spp.). Additionally, we will use ancient DNA sequencing of late Pleistocene and Holocene specimens of the extinct bluebuck (H. leucophaeus) in order to test the hypothesis that this species already had a non-viable population size at the end of the 18th century, meaning hunting with firearms by European settlers was only an incidental contributor to its demise. We will also compare genetic variation among eastern and western South African sites in order to assess whether the bluebuck was an east-west migrating species and whether climatic changes at the onset of the Holocene contributed to its eventual extinction by disrupting its migration patterns.