ADVANCE Fellows Award: Patterns of Biomineralization and Isotopic Variations in the Teeth and Bones of Modern Bison

随着人们对破译影响地球气候的因素的兴趣日益浓厚，研究人员已经开发出几种可用于重建古代环境条件的替代方法。重建短期（季节到年度）环境波动最有前途的工具之一是脊椎动物化石的同位素分析。对野牛化石的分析为这类研究带来了特别的希望。然而，目前基于化石野牛分析的古环境重建的精度有限，因为：(1)没有详细研究野牛牙齿内牙釉质生物矿化速率；(2)现代野牛的d18O和d13C值与当地环境条件的精确关系尚未精确量化。该项目的目的是量化野牛的同位素分析如何精确地用于重建古环境条件。本研究的第一部分将记录保存在野牛牙釉质中的生物矿化和同位素变化模式，以便制定最佳采样策略。本研究的第二部分将量化现代大平原野牛的d18O和d13C值与环境变化的相关性，包括：平均温度、季节温度范围、降水、相对湿度和草地成分（即C3/C4比）。因此，这项研究将量化对野牛d18O和d13C值的精确分析，以重建当地环境的年度和季节变化。它将绘制出现代野牛的同位素梯度图，这将作为解释野牛化石和其他食草动物中保存的同位素信号的基线。该研究将大大提高草食动物化石同位素分析重建古气候和古植被的精度和准确性。

As interest grows in deciphering the factors that influence the Earth's climate, researchers have developed several proxies useful for reconstructing ancient environmental conditions. One of the most promising tools for reconstructing short-term (seasonal to annual) environmental fluctuations is isotopic analysis of vertebrate fossils. Analyses of fossil bison hold particular promise for such research. However, the precision of paleoenvironmental reconstructions based on analyses of fossil bison is currently limited because: (1) the rate of enamel biomineralization within bison teeth has not been studied in detail, and (2) the precise relationship between the d18O and d13C values of modern bison and local environmental conditions has not been precisely quantified. The purpose of this project is to quantify how precisely isotopic analyses of bison can be used to reconstruct paleoenvionemtal conditions. The first part of this study will document the patterns of biomineralization and isotope variations preserved within bison tooth enamel in order to develop an optimal sampling strategy. The second part of this study will quantify how well the d18O and d13C values of modern Great Plains bison correlate with environmental changes including: average temperature, seasonal temperature range, precipitation, relative humidity, and grassland composition (i.e., C3/C4 ratio). This study will thus quantify how precisely analyses of the d18O and d13C values of bison can be used to reconstruct annual and seaonal variations in local environments. It will produce a map of the isotope gradients in modern bison, which will serve as a baseline for interpreting the isotope signals preserved in fossil bison as well as other herbivores. This study will thus greatly increase the precision and accuracy of paleoclimatic and paleovegetation reconstruction based on isotope analyses of fossil herbivores.