Data_Sheet_1_Carbon, nitrogen, and oxygen stable isotopes in modern tooth enamel: A case study from Gorongosa National Park, central Mozambique.pdf

The analyses of the stable isotope ratios of carbon (δ13C), nitrogen (δ15N), and oxygen (δ18O) in animal tissues are powerful tools for reconstructing the feeding behavior of individual animals and characterizing trophic interactions in food webs. Of these biomaterials, tooth enamel is the hardest, most mineralized vertebrate tissue and therefore least likely to be affected by chemical alteration (i.e., its isotopic composition can be preserved over millions of years), making it an important and widely available archive for biologists and paleontologists. Here, we present the first combined measurements of δ13C, δ15N, and δ18O in enamel from the teeth of modern fauna (herbivores, carnivores, and omnivores) from the well-studied ecosystem of Gorongosa National Park (GNP) in central Mozambique. We use two novel methods to produce high-precision stable isotope enamel data: (i) the “oxidation-denitrification method,” which permits the measurement of mineral-bound organic nitrogen in tooth enamel (δ15Nenamel), which until now, has not been possible due to enamel’s low organic content, and (ii) the “cold trap method,” which greatly reduces the sample size required for traditional measurements of inorganic δ13Cenamel and δ18Oenamel (from ≥0.5 to ≤0.1 mg), permitting analysis of small or valuable teeth and high-resolution serial sampling of enamel. The stable isotope results for GNP fauna reveal important ecological information about the trophic level, dietary niche, and resource consumption. δ15Nenamel values clearly differentiate trophic level (i.e., carnivore δ15Nenamel values are 4.0‰ higher, on average, than herbivores), δ13Cenamel values distinguish C3 and/or C4 biomass consumption, and δ18Oenamel values reflect local meteoric water (δ18Owater) in the park. Analysis of combined carbon, nitrogen, and oxygen stable isotope data permits geochemical separation of grazers, browsers, omnivores, and carnivores according to their isotopic niche, while mixed-feeding herbivores cannot be clearly distinguished from other dietary groups. These results confirm that combined C, N, and O isotope analyses of a single aliquot of tooth enamel can be used to reconstruct diet and trophic niches. Given its resistance to chemical alteration, the analysis of these three isotopes in tooth enamel has a high potential to open new avenues of research in (paleo)ecology and paleontology.

对动物组织中碳（δ¹³C）、氮（δ¹⁵N）和氧（δ¹⁸O）稳定同位素比值的分析，是重建单个动物摄食行为、解析食物网内营养级相互作用的有力工具。在各类生物材料中，牙釉质是脊椎动物体内最坚硬、矿化程度最高的组织，因此最不易受到化学蚀变影响——即其同位素组成可在数百万年内得以保存，成为生物学家与古生物学家重要且易于获取的研究保藏库。本研究首次报道了采自莫桑比克中部研究程度极高的戈龙戈萨国家公园（GNP）现代动物群（包括草食动物、肉食动物与杂食动物）牙齿牙釉质中δ¹³C、δ¹⁵N和δ¹⁸O的联合测定数据。我们采用两种创新方法获取高精度牙釉质稳定同位素数据：其一为“氧化-反硝化法”，可实现牙釉质中矿物结合态有机氮（δ¹⁵N_牙釉质）的测定——此前由于牙釉质有机含量极低，该类测定始终无法实现；其二为“冷阱法”，可大幅降低传统无机牙釉质δ¹³C与δ¹⁸O测定所需的样本量（从≥0.5 mg降至≤0.1 mg），从而支持小型或珍贵牙齿的分析以及牙釉质的高分辨率连续采样。戈龙戈萨国家公园动物群的稳定同位素结果揭示了与营养级、摄食生态位及资源利用相关的关键生态学信息：牙釉质δ¹⁵N值可清晰区分不同营养级（例如，肉食动物的牙釉质δ¹⁵N值平均较草食动物高出4.0‰）；牙釉质δ¹³C值可区分C3与/或C4生物质的摄入；牙釉质δ¹⁸O值可反映公园内当地大气降水的δ¹⁸O组成。对碳、氮、氧稳定同位素联合数据的分析，可依据同位素生态位对草食啃食者、食叶动物、杂食动物与肉食动物进行地球化学区分，但混合摄食的草食动物无法与其他膳食类群清晰区分。上述结果证实，对单份牙釉质样品开展碳、氮、氧同位素联合分析，可用于重建动物的饮食结构与营养生态位。鉴于牙釉质抗化学蚀变的特性，对牙釉质中这三种同位素的分析具有极大潜力，可为（古）生态学与古生物学领域开辟全新的研究方向。