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

更新世气候循环在高纬度产生冰期-间冰期气候，在低纬度产生湿润-干旱气候循环。通过地质和孢粉学研究，非洲这种大约10万年的低纬度循环变化变得越来越清晰，它们的影响也通过对非洲食草动物物种的系统地理学研究间接推断出来。在此，我们建议通过全基因组测序利用种群规模历史来测试更新世湿-干旱循环对非洲大型哺乳动物分布扩张和收缩的影响程度。重点分类群是Hippotragini，这是一个由8个历史上现存的物种组成的分支，跨越沙漠到草原生物群系。我们将验证干旱适应物种（Oryx + Addax）在干旱阶段（冰川高峰）经历最大种群规模的假设。对更依赖水的类群（Hippotragus spp.）进行了相反的预测。此外，我们将对已灭绝的蓝鹿（H. leucophaeus）的晚更新世和全新世标本进行古代DNA测序，以检验这个物种在18世纪末已经有一个不可生存的种群规模的假设，这意味着欧洲定居者用火器狩猎只是导致其灭亡的一个偶然因素。我们还将比较南非东部和西部地区的遗传变异，以评估蓝羚是否是一种东西向迁徙的物种，以及全新世开始时的气候变化是否会破坏其迁徙模式，从而导致其最终灭绝。

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.