Enamel Maturation in Mammals and Implications for Stable Isotope Analysis for Diet and Climate Signals

该项目的重点是研究哺乳动物的同位素组成的时间变化如何记录在发育中的牙釉质中。牙齿从牙冠到牙根逐渐形成，并作为动物血液碳酸氢盐库中季节性同位素变化的记录者。 这种变化反过来又与气候、食物供应、迁徙、生态系统相互作用和其他环境条件的季节性变化有关。 化石牙釉质中保存有同位素信号，因此牙齿是短时间尺度上古代季节性和环境变化的重要档案。 尽管广泛使用的牙齿内同位素的方法，有相当大的不确定性，如何测量的信号与动物水库内的变化的实际信号。 这种不确定性源于对通常研究的牙齿中釉质矿物质沉积和积累的时间和空间模式的认识不足。 虽然有前途，牙齿内同位素的方法将继续妥协，直到这些不确定性得到解决的古指标。我们将使用微型计算机断层扫描（microCT），以调查时间和空间模式的釉质矿物质积累在不同年龄的动物从一系列物种的牙齿发育。 根据microCT数据确定的成熟参数将能够开发牙齿和物种特异性模型，这些模型描述了如何将主要输入信号记录为牙齿内同位素分布。 将开发逆模型，允许根据测得的同位素数据和成熟参数的知识估计主要输入信号。 模型结果与研究动物中已知的同位素变化之间的比较将允许直接评估这些模型的准确性。具体而言，本研究将提供羊驼（羊驼）、山羊（山羊）和牛（奶牛）牙列的成熟参数。 这些动物在牙齿形成过程中经历了严格控制的同位素变化，因此本研究将显示基于成熟参数的正向和反向模型在多大程度上允许重建主要输入信号。 这些物种跨越了一系列的偶蹄目内的多样性，并将显示是否一般模型可以适用于许多物种在这个命令。智力上的优点。这项研究将大大增加对各种研究人员使用的基本工具的理解。 microCT、正演建模和反演建模方法将立即用于使用牙内同位素方法的研究人员。 本研究的成果为其他研究者提供了正、反演建模的经验，拓宽了研究的科学背景，对今后的研究具有一定的借鉴意义。 由于这项研究，牙齿内方法的进展将有助于我们进一步了解古代人类的环境和文化，灭绝物种的行为和生态系统背景，以及古代气候和环境。 更广泛的影响。 这项研究将形成本杰明·帕西的博士论文。 他将负责这项研究的设计，执行和传播，并将学习项目管理，实验室实践，数据评估和专业沟通方面的宝贵技能。 一名本科生将参与该项目的实验室方面。 这个人将获得宝贵的第一手研究经验，并有机会参加专业会议，介绍成果

The focus of this project is to study how temporal changes in the isotopic composition of mammals are recorded in developing tooth enamel. Teeth form progressively from crown to root and act as recorders of seasonal isotopic variation in the animal blood bicarbonate reservoir. This variation is in turn related to seasonal variations in climate, food availability, migration, ecosystem interactions, and other environmental conditions. Isotopic signals are preserved in fossil tooth enamel, so teeth are important archives of ancient seasonality and environmental variation on short time scales. Despite the wide usage of intra-tooth isotope approaches, there is considerable uncertainty as to how the measured signals relate to actual signals of variation within the animal reservoir. This uncertainty stems from inadequate knowledge of the temporal and spatial patterns of enamel mineral deposition and accumulation in teeth that are commonly studied. Although promising, the intra-tooth isotope method will remain compromised as a paleoindicator until these uncertainties are addressed. We will use micro-computed tomography (microCT) to investigate the temporal and spatial pattern of enamel mineral accumulation in developing teeth of animals of various ages from a range of species. Maturation parameters determined from the microCT data will enable development of tooth- and species-specific models that describe how primary input signals are recorded as intra-tooth isotopic profiles. Inverse models will be developed that allow estimates of primary input signals based on measured isotope data and knowledge of maturation parameters. Comparison between model results and known isotopic changes in the animals studied will allow direct evaluation of the accuracy of these models. Specifically, this study will provide maturation parameters for dentitions of Alpaca (alpaca), Capra (goat), and Bos (cow). These animals underwent strictly controlled isotopic changes during tooth formation, and therefore this study will show the extent to which forward and inverse models based on maturation parameters allow for reconstruction of primary input signals. These species span a range of diversity within the artiodactyla and will show whether general models can be applied to many species within this order. Intellectual merit. This study will significantly increase the understanding of a basic tool used by a wide variety of researchers. The microCT, forward modeling, and inversion modeling methods will be of immediate use to researchers using the intra-tooth isotope method. Forward and inverse modeling learned by other researchers as a result of this study will broaden scientific background and benefit future studies. Advances in the intra-tooth method owing to this study will help advance our understanding of ancient human environments and cultures, behavior and ecosystem context of extinct species, and ancient climates and environments. Broader impact. This research will form the Ph.D dissertation of Benjamin Passey. He will be responsible for the design, execution, and dissemination of this research and will learn valuable skills in project management, laboratory practice, data evaluation, and professional communication. An undergraduate student will be involved in laboratory aspects of this project. This person will gain invaluable first-hand research experience and have opportunities to attend professional meetings to present results