Stoffel Céline, Dufresnes Christophe, Okello John B A, Noirard Christian, Joly Pierre, Nyakaana Silvester, Muwanika Vincent B, Alcala Nicolas, Vuilleumier Séverine, Siegismund Hans R, Fumagalli Luca
Department of Ecology and Evolution, Laboratory for Conservation Biology, University of Lausanne, Biophore Building, 1015, Lausanne, Switzerland.
Mol Ecol. 2015 May;24(10):2507-20. doi: 10.1111/mec.13179. Epub 2015 Apr 22.
Over the past two decades, an increasing amount of phylogeographic work has substantially improved our understanding of African biogeography, in particular the role played by Pleistocene pluvial-drought cycles on terrestrial vertebrates. However, still little is known on the evolutionary history of semi-aquatic animals, which faced tremendous challenges imposed by unpredictable availability of water resources. In this study, we investigate the Late Pleistocene history of the common hippopotamus (Hippopotamus amphibius), using mitochondrial and nuclear DNA sequence variation and range-wide sampling. We documented a global demographic and spatial expansion approximately 0.1-0.3 Myr ago, most likely associated with an episode of massive drainage overflow. These events presumably enabled a historical continent-wide gene flow among hippopotamus populations, and hence, no clear continental-scale genetic structuring remains. Nevertheless, present-day hippopotamus populations are genetically disconnected, probably as a result of the mid-Holocene aridification and contemporary anthropogenic pressures. This unique pattern contrasts with the biogeographic paradigms established for savannah-adapted ungulate mammals and should be further investigated in other water-associated taxa. Our study has important consequences for the conservation of the hippo, an emblematic but threatened species that requires specific protection to curtail its long-term decline.
在过去二十年中，越来越多的系统发育地理学研究极大地增进了我们对非洲生物地理学的理解，尤其是更新世多雨-干旱循环对陆地脊椎动物所起的作用。然而，对于面临不可预测水资源供应所带来巨大挑战的半水生动物的进化历史，我们仍然知之甚少。在本研究中，我们利用线粒体和核DNA序列变异以及广泛的样本采集，探究了普通河马（Hippopotamus amphibius）在晚更新世的历史。我们记录到大约在0.1 - 0.3百万年前发生了一次全球范围的种群数量和空间扩张，这很可能与一次大规模排水溢流事件有关。这些事件大概促成了历史上河马种群在整个大陆范围内的基因流动，因此，如今已不存在明显的大陆尺度的遗传结构。尽管如此，现今的河马种群在基因上是隔离的，这可能是全新世中期干旱化和当代人为压力造成的结果。这种独特模式与为适应草原的有蹄类哺乳动物所确立的生物地理学范式形成对比，应当在其他与水相关的分类群中进一步研究。我们的研究对于河马的保护具有重要意义，河马是一种标志性但濒危的物种，需要特定保护措施来遏制其长期数量下降。
