Natural Trap Cave Revisited: Ancient DNA, Climate and the Megafaunal Extinction

冰河时代的末期（大约11000年前）是北美发生巨变的时期。许多大型哺乳动物物种连同它们的栖息地一起灭绝了。气候在这次灭绝事件中发挥了重要作用，目前的气候变化继续影响和改变着今天的世界。该项目将分析来自怀俄明州自然陷阱洞穴的冰河时代动物的古代DNA，以研究这些过去的气候变化与遗传变异和灭绝之间的关系。这项研究将使人们更好地全面了解气候变化与人口结构、遗传变异变化以及最终灭绝之间的关系，这可能对生物学家如何思考和减轻目前正在发生的人类引起的气候变化产生潜在影响。该项目还将为科学参与和向公众和课堂环境推广提供许多机会。挖掘和最终发现的有趣性质使这次探险成为通过印刷和电视媒体向公众介绍科学的绝佳机会。此外，这是一个很好的机会，让高中生实时体验如何进行实地科学。通过网络上的远程参与，这个项目将让学生有机会在一个安全的、虚拟的环境中，参与到挖掘化石遗址的体验中，在野外生活，挖掘出巨大的、死亡已久的野兽的骨头。【技术摘要】更新世末期是北美洲发生巨变的时期。许多大型哺乳动物物种灭绝，各种相关生态系统也随之消失。气候在这次灭绝事件中发挥了重要作用，目前的气候变化仍在影响和改变着今天的生态系统。该项目将重新开放怀俄明州北部的天然陷阱洞穴，以调查气候变化对古生态的反应，以及这与更新世末期巨型动物灭绝事件的关系。NTC永久的寒冷和潮湿的环境保存了大量的巨型动物骨骼，其中仍然含有古老的DNA （aDNA）和胶原蛋白分子。这种罕见的资源是在更新世末灭绝事件之前、期间和之后的关键阶段进行种群水平遗传变异分析的最佳选择。本项目研究的关键问题包括：1)更新世灭绝事件是在遗传多样性大量丧失之前发生的，还是同时发生的？2)更新世/全新世边界的形态变化是适应的产物还是移民的产物？3)形态和遗传变异的重大转变是否与气候变化相关？利用aDNA、AMS放射性碳测年、稳定同位素分析、形态分析和NTC以前的数据，该项目将研究气候条件的变化及其与遗传多样性和形态变化的关系。这项研究将有助于更好地了解气候变化如何导致物种灭绝，并可能揭示气候变化、超种群结构以及遗传和形态变异变化之间的相关性。

Non-technical abstractThe end of the ice age (about 11,000 years ago) was a time of radical change in North America. Many species of large mammals went extinct, along with their habitats. Climate played a major role in this extinction event and current climate change continues to affect and alter the world today. This project will analyze ancient DNA from ice age animals from Natural Trap Cave, Wyoming to examine how these past climate changes relate to genetic variability and extinction. This research will lead to a better overall understanding of how climate change is related to population structure, changes in genetic variation, and ultimately extinction, which may have potential effects on how biologists think about and mitigate the current human-caused climate change occurring today. This project will also provide many opportunities for scientific engagement and outreach to both the general public and in classroom settings. The intriguing nature of the excavations and ultimate findings make this expedition a perfect opportunity to bring science to the general public through print and television media. Additionally, this is an excellent opportunity to give high school students real time experience on how field science is performed. Via remote participation on the web, this project will give students the opportunity to participate in the experience of what it is like to excavate a fossil site, live out in the field, and unearth bones of gigantic, long-dead beasts, but in a safe, virtual setting.Technical abstractThe end-Pleistocene was a time of radical change in North America. Many species of large mammals went extinct, along with the loss of a variety of associated ecosystems. Climate played a major role in this extinction event and current climate change continues to affect and alter ecosystems today. This project will re-open Natural Trap Cave in northern Wyoming to investigate paleoecological responses to climate change and how this relates to the megafaunal extinction events at the end of the Pleistocene. The permanently cold and moist conditions at NTC have preserved a large collection of megafaunal bones which still contain ancient DNA (aDNA) and collagen molecules. This rare resource is optimal to perform population-level analyses of genetic variation in the critical phases before, during, and after the end-Pleistocene extinction events. Key questions investigated in this project include: 1) Was the Pleistocene extinction event preceded by, or concurrent with a large loss of genetic diversity? 2) Are morphological changes at the Pleistocene/Holocene boundary the product of adaptation, or immigration? 3) Are major shifts in morphological and genetic variation correlated with climate change? Using aDNA, AMS radiocarbon dates, stable isotope analyses, morphological analyses, and previous data from NTC this project will investigate changes in climatic conditions and how they correlate with genetic diversity and morphological change. This research will lead to a better understanding of how climate change drives extinction and may reveal correlations between climate change, metapopulation structure and changes in genetic and morphological variation.