Flow cytometric techniques in Quaternary research: Improving radiocarbon age determination and evaluating potentials of stable isotope and aDNA analyses based on high-purity fossil pollen samples

第四纪研究中的流式细胞术：改进放射性碳年龄测定并评估基于高纯度化石花粉样品的稳定同位素和 aDNA 分析的潜力

• 批准号: 400195333
• 负责人: Dr. Christian Leipe
• 金额: --
• 依托单位: University of Nagoya
• 依托单位国家: 德国
• 项目类别: Research Fellowships
• 财政年份: 2018
• 资助国家: 德国
• 起止时间: 2017-12-31 至 2020-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/400195333?language=en
• 关键词: Flow; cytometric; techniques; Quaternary; research

The analysis of fossil pollen assemblages (i.e. pollen analysis = PA) is one of the most frequently used methods in Quaternary research and has significantly contributed to our understanding of past environmental changes, human–environment interactions, land use history and the origin and spread of agriculture. The existing pollen-based reconstructions, including qualitative and quantitative approaches, take into account the absence/presence of indicator-taxa and/or the taxa percentages in the examined sediment samples. Recent studies have indicated potential of pollen-derived stable isotope and ancient DNA (aDNA) records for Quaternary research. Stable isotope signals of terrestrial pollen have been suggested as a new palaeoclimate proxy that would overcome the time lag between climate change and vegetation response. The latter is a serious constraint in PA, particularly in high-resolution studies. Pollen aDNA has shown to be capable for identifying source plants to species level, which is seldom possible by traditional PA and would allow precise identification of ecological/climatic indicator taxa, ancient domesticates, and spread of crops. The application of fossil pollen in radiocarbon dating helps to overcome errors in age determination due to reservoir effects, which most sedimentary archives suffer from. All mentioned research methods require effective extraction of pure pollen concentrates comprising entire spectra or selected taxa. My own preliminary investigations and the experiments of colleagues have shown that flow cytometry is a promising approach to accomplish this task. In this project, I will first focus on extracting clean, contamination-free pollen fractions from the well-dated and reservoir-free upper part (0–6000 years before present) of the Lake Kushu (northern Japan) RK12 sediment core based on flow cytometry using different technical approaches and devices. In a second step, I will measure stable isotope compositions (δ13C and δ18O) of selected pollen taxa (e.g. fir and oak) fractions extracted from the RK12 core. DNA analysis will be tested for detection of selected ecological indicator species and domesticated crops including barley and millets. I will also perform radiocarbon dating on pollen concentrates. The results will be compared with those obtained using conventional techniques on the RK12 core. If these tests are completed successfully, in a third step, the methods will be applied to different sediment sections from East and Southeast Asia comprising the lower, less well dated part of RK12 and one each from central Japan and northern Vietnam. These applications aim at optimizing workflows and gaining deeper insights into the evolution of the East Asian summer monsoon and short-term climate variations during the late-glacial–Holocene interval. Moreover, I intend to detect the cultivation/spread of different domesticated plants (barley, millets, rice).

化石花粉组合分析(即花粉分析)是第四纪研究中最常用的方法之一，它有助于我们理解过去的环境变化、人类与环境的相互作用、土地利用历史和农业的起源和传播。现有的以花粉为基础的重建，包括定性和定量方法，考虑到所检查的沉积物样品中没有/存在指示性分类群和/或分类群的百分比。最近的研究表明，花粉来源的稳定同位素和古代DNA(ADNA)记录可能用于第四纪研究。陆地花粉的稳定同位素信号被认为是一种新的古气候指标，可以克服气候变化和植被响应之间的时间滞后。后者在PA中是一个严重的制约因素，特别是在高分辨率研究中。花粉aDNA已被证明能够在物种水平上识别来源植物，这在传统的PA中是很难做到的，并且可以精确地识别生态/气候指示类群、古老的家养动物和作物的传播。化石花粉在放射性碳测年中的应用有助于克服由于储集层效应造成的测年误差，这是大多数沉积档案所受的影响。所有提到的研究方法都需要有效地提取纯花粉浓缩物，包括整个光谱或选定的分类群。我自己的初步调查和同事的实验表明，流式细胞术是完成这一任务的一种有前途的方法。在这个项目中，我首先将重点放在使用不同的技术方法和设备基于流式细胞术从久治湖(日本北部)RK12沉积岩芯上部(距今0-6000年)提取干净、无污染的花粉组分。在第二步中，我将测量从RK12岩心提取的选定花粉分类群(例如冷杉和橡木)的稳定同位素组成(δ13C和δ18O)。DNA分析将用于检测选定的生态指示物种和驯化作物，包括大麦和谷子。我还将对花粉浓缩物进行放射性碳测年。结果将与在RK12堆芯上使用常规技术获得的结果进行比较。如果这些测试成功完成，在第三步，这些方法将应用于来自东亚和东南亚的不同沉积物部分，包括RK12较低、年代较差的部分，以及来自日本中部和越南北部的各一段。这些应用程序旨在优化工作流程，并更深入地了解东亚夏季风的演变和晚冰川-全新世期间的短期气候变化。此外，我打算检测不同驯化植物(大麦、谷子、水稻)的栽培/传播情况。