Forward and inverse methods for extracting climate and diet information from stable isotope profiles in proboscidean molars
Forward and inverse methods for extracting climate and diet information from stable isotope profiles in proboscidean molars
复制标题
从长鼻磨牙的稳定同位素谱中提取气候和饮食信息的正向和逆向方法
DOI：
10.1016/j.quaint.2020.06.030
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发表时间：
2020
影响因子：
2.2
通讯作者：
T. Cerling
中科院分区：
文献类型：
--
作者：
K. Uno;D. Fisher;G. Wittemyer;I. Douglas;Nancy P Carpenter;P. Omondi;T. Cerling
牙釉质中的牙内稳定同位素分布提供了饮食和环境信息的时间序列，如果正确解释，这些信息可以作为过去环境中季节变化的档案。解释这些剖面的一个主要挑战来自牙釉质矿化和发育几何学所赋予的时间平均，其中主要（δ13C或δ18O）输入信号被衰减和转移，这可能导致对季节变化的幅度或频率的错误解释。已经开发了几种正向和逆向模型来重建来自连续生长的牙齿的齿内轮廓的主要输入信号。这里的模型由 Passey 和 Cerling (2002) 以及 Passey 等人开发。 (2005) 扩展到象象亚科的臼齿，它们的生长时间间隔很长但有限。长鼻类臼齿对于牙内轮廓特别有吸引力，因为它们可能包含十年或更长时间的信息，并且由于牙釉质厚且尺寸大，它们通常在化石记录中保存完好。通过对现存非洲象 (Loxodonta africana) 和猛犸象 (Mammuthus columbi) 的臼齿薄片进行组织学分析以及对猛犸象 (Mammuthus columbi) 进行显微 CT 分析，建立正向模型参数。非洲磨牙板。未成熟牙釉质的密度约为成熟牙釉质最终密度的65%。同位长度约为 35 至 55 毫米，成熟长度约为 70 毫米。组织学方法用于确定大象和猛犸象臼齿板的牙冠形成时间（CFT）。在薄切片中研究的大象和猛犸象臼齿板的 CFT 约为 5-6 年和 11 年，这意味着平均增长率分别约为 21 毫米/年和 16 毫米/年。比较了动物园大象的同期臼齿和象牙轮廓。象牙同位素剖面充当主要输入信号的代理，从而提供评估正向和逆向模型的机会。动物园大象概况的结果表明，逆模型准确地重建了主要输入信号的幅度和整体结构。猛犸象摩尔轮廓的反演模型结果显示，测量的牙釉质轮廓中 δ13C 的范围是其两倍。反演模型结果表明，改进主要输入信号的重建可以更准确地解释饮食和身体水分的季节变化，进而更准确地解释过去环境中的植被和降水。
Intratooth stable isotope profiles in enamel provide time series of dietary and environmental information that if correctly interpreted, serve as archives of seasonal variability in past environments. A major challenge in interpreting these profiles arises from time averaging imparted by enamel mineralization and developmental geometry, whereby the primary (δ13C or δ18O) input signal is attenuated and shifted, which can potentially lead to incorrect interpretations of the magnitude or frequency of seasonal variability. Several forward and inverse models have been developed to reconstruct the primary input signal from intratooth profiles in continuously growing teeth. Here the models developed by Passey and Cerling (2002) and Passey et al. (2005) are extended to molars of Elephantinae, which grow over a long but finite interval of time. Proboscidean molars are particularly attractive for intratooth profiles because they may contain a decade or more of information and they are often well preserved in the fossil record because of their thick enamel and large size.Forward model parameters are established using histological analysis of molar thin sections of extant African elephants (Loxodonta africana) and a mammoth (Mammuthus columbi) and by micro-CT analysis ofL. africanamolar plates. The density of immature enamel is about 65% of the final density of mature enamel. The appositional length varies from approximately 35 to 55 mm, and the maturation length is about 70 mm. Histological methods are used to determine crown formation time (CFT) in elephant and mammoth molar plates. CFT for the elephant and mammoth molar plates studied in thin section are about 5–6 years and 11 years, which translate to mean growth rates of about 21 mm/year and 16 mm/year, respectively.Coeval molar and tusk profiles from a zoo elephant are compared. The tusk isotope profile serves as a proxy for the primary input signal, and thus provides an opportunity to evaluate the forward and inverse models. The results from the zoo elephant profiles demonstrate that the inverse model accurately reconstructs the amplitude and overall structure of the primary input signal. Inverse model results of mammoth molar profiles show double the range of δ13C in measured enamel profiles. Inversion model results illustrate that improved reconstruction of the primary input signal can lead to more accurate interpretations of the seasonal variability of diet and body water and by extension, vegetation and precipitation in past environments.