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

更新世气候旋回在高纬度产生了冰川-间冰期气候，在低纬度产生了潮湿-干旱循环。通过地质学和孢粉学研究，非洲这种大约10万年的低纬度周期性变化正在变得更加清楚，其影响也通过对非洲草食物种的系统地理研究间接推断出来。我们在这里建议通过全基因组测序来使用种群规模历史来测试更新世湿润干旱循环对非洲大型哺乳动物分布的扩张和收缩的影响。焦点的分类单元是希波特拉吉尼，一个分支，有8个历史上存在的物种，横跨沙漠到大草原生物群。我们将验证这样的假设，即适应干旱的物种(Oryx+Addax)在干旱阶段(冰川高峰期)经历了最大的种群规模。对于更依赖于水的分类群(Hippotangus spp.)，则做出了相反的预测。此外，我们将使用已灭绝的蓝鲸(H.leucophaeus)晚更新世和全新世标本的古代DNA测序，以检验该物种在18世纪末已经不再有生存种群规模的假设，这意味着欧洲定居者的枪支狩猎只是其灭绝的一个附带因素。我们还将比较南非东部和西部地点之间的遗传变异，以评估蓝知更鸟是否是东西方迁徙物种，以及全新世开始时的气候变化是否通过扰乱其迁徙模式而导致其最终灭绝。

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.