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

这个项目的重点是研究哺乳动物同位素组成的时间变化是如何在发育中的牙釉质中记录下来的。牙齿从牙冠到牙根逐渐形成，并作为动物血液碳酸氢盐储存库中季节性同位素变化的记录器。这种变化又与气候、食物可获得性、迁徙、生态系统相互作用和其他环境条件的季节变化有关。化石牙釉质中保存着同位素信号，因此牙齿是古季节性和短时间尺度环境变化的重要档案。尽管牙内同位素方法被广泛使用，但对于测量信号如何与动物储藏室内的实际变异信号相关仍有相当大的不确定性。这种不确定性源于对通常研究的牙釉质矿物质沉积和积累的时间和空间模式的了解不足。尽管前景看好，但在这些不确定性被解决之前，牙内同位素方法作为一种古指示器仍将受到损害。我们将使用微型计算机断层扫描(MicroCT)来研究不同物种不同年龄动物发育中牙釉质矿物质积累的时间和空间模式。根据microCT数据确定的成熟参数将使牙齿和物种特定模型的开发成为可能，这些模型描述了主要输入信号是如何记录为牙齿内同位素分布的。将开发反向模型，允许根据测量的同位素数据和成熟度参数的知识估计主要输入信号。将模型结果与所研究动物的已知同位素变化进行比较，可以直接评估这些模型的准确性。具体地说，这项研究将提供羊驼(羊驼)、山羊(山羊)和牛(奶牛)的牙列成熟参数。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，因此这项研究将展示基于成熟参数的正反向模型允许重建主要输入信号的程度。这些物种跨越了偶蹄目内的一系列多样性，并将表明一般模型是否可以适用于该目中的许多物种。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。使用牙内同位素方法的研究人员将立即使用MicroCT、正演模拟和反演模拟方法。通过本研究，其他研究人员学习到的正反向建模将拓宽科学背景，对未来的研究有所裨益。这项研究在牙内方法方面的进展将有助于我们加深对古代人类环境和文化、灭绝物种的行为和生态环境以及古代气候和环境的理解。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，并将在项目管理、实验室实践、数据评估和专业沟通方面学习宝贵的技能。一名本科生将参与这个项目的实验室方面。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来展示结果。

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