Collaborative Research: A Paleogenetic Survey of Late Quaternary Mammal Biodiversity in Southeast Alaska

合作研究：阿拉斯加东南部晚第四纪哺乳动物生物多样性的古遗传学调查

• 批准号: 1556565
• 负责人: Charlotte Lindqvist
• 金额: $ 15万
• 依托单位: SUNY at Buffalo
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-03-01 至 2019-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1556565&HistoricalAwards=false
• 关键词: Collaborative; Research; Paleogenetic; Survey; Late

The Pleistocene Epoch began approximately 1.8 million years before present and lasted until about 12 milennia ago, when the last Ice Age ended. Many large mammals succumbed to the harsh climatic conditions of this period, while others were confined to habitable ice-free areas, or refugia. During the peak of the last Ice Age, sheets of ice divided the Old and New Worlds, restricting movement of organisms across the Bering Land Bridge for thousands of years. Geological and biological evidence have suggested, however, that refugia along the North Pacific Coast may have played crucial roles as "stepping stones" for movements of species between the Old and New Worlds, forming an early postglacial corridor for the recolonization of North America. Building on an unparalleled vertebrate bone collection excavated from limestone caves in Southeast (SE) Alaska, this project will perform genetic analyses and radiocarbon dating of black and brown bear specimens from throughout the last 50,000 years to directly test if these caves were occupied by bears at the peak of the last Ice Age. By ensuring precise species determinations of these keystone mammal species in SE Alaska, and providing evolutionary links to extant populations, this research will elucidate species' responses to climate change and help circumscribe the extent and timing of viable coastal refugia in SE Alaska. As such, results from this project will provide important data for a deeper comprehension of the dynamic changes in trans-Beringian biota during the Late Pleistocene, the diversity and biogeographic history of the region, and its importance as a corridor for exchange between continents during and after the last Ice Age.An important outcome of this research is to recover genetic information from bear specimens that occupied SE Alaska during the late Wisconsin glaciation and into the Holocene, and provide calibrations for precise timings of demographic events. Focusing on brown bears (Ursus arctos) and black bears (Ursus americanus), which have developed into well-established systems for studies of Northern Hemisphere phylogeography, the project will test if the same bear populations inhabited this region continuously for the last 50,000 years, or if they were recolonized following the Last Glacial Maximum, and if they contributed to postglacial (modern) mainland populations. The project will take a highly integrative approach that leverages state-of-the-art ancient DNA analysis (including a targeted hybridization enrichment approach using custom-made biotinylated RNA baits designed from whole mitochondrial genome sequences), radiocarbon and molecular dating, reconstruction of paleodiets, and phylogenetic reconstruction. This research will have broad significance toward understanding past and present North American mammal diversity and for assessing the impact of late Pleistocene climate change on biotic diversification, colonization, and the historical biogeography of the region.

更新世开始于大约 180 万年前，一直持续到大约 1200 万年前，最后一个冰河时代结束。许多大型哺乳动物死于这一时期的恶劣气候条件，而另一些则被限制在可居住的无冰地区或避难所。在上一个冰河时代的高峰期，冰层将新旧世界分开，数千年来限制了生物体穿过白令陆桥的活动。然而，地质和生物学证据表明，北太平洋沿岸的避难所可能作为物种在新旧世界之间移动的“踏脚石”发挥了至关重要的作用，形成了北美重新殖民化的早期冰河期走廊。该项目以阿拉斯加东南部石灰岩洞穴中出土的无与伦比的脊椎动物骨骼为基础，将对过去 5 万年的黑熊和棕熊标​​本进行遗传分析和放射性碳测年，以直接测试这些洞穴是否曾被熊占据过。上一个冰河时代的顶峰。通过确保对阿拉斯加东南部这些关键哺乳动物物种进行精确的物种测定，并提供与现存种群的进化联系，这项研究将阐明物种对气候变化的反应，并帮助限制阿拉斯加东南部可行的沿海保护区的范围和时间。因此，该项目的结果将为更深入地理解晚更新世跨白令海峡生物群的动态变化、该地区的多样性和生物地理历史及其作为大陆间交流走廊的重要性提供重要数据。最后一个冰河时代之后。这项研究的一个重要成果是从威斯康星州冰川晚期和全新世时期占据阿拉斯加东南部的熊标本中恢复遗传信息，并为精确的时间提供校准人口事件。该项目将重点关注棕熊 (Ursus arctos) 和黑熊 (Ursus americanus)，它们已发展成为北半球系统发育地理学研究的完善系统，该项目将测试相同的熊种群是否在过去 5 万年中连续居住在该地区，或者他们是否在末次盛冰期之后重新殖民，以及他们是否对后冰期（现代）大陆人口做出了贡献。该项目将采用高度综合的方法，利用最先进的古代 DNA 分析（包括使用根据整个线粒体基因组序列设计的定制生物素化 RNA 诱饵的靶向杂交富集方法）、放射性碳和分子测年、古饮食重建，和系统发育重建。这项研究对于了解过去和现在的北美哺乳动物多样性以及评估更新世晚期气候变化对该地区生物多样性、殖民化和历史生物地理学的影响具有广泛的意义。