Krajcarz Maciej T, Krajcarz Magdalena, Drucker Dorothée G, Bocherens Hervé
Institute of Geological Sciences, Polish Academy of Sciences, Research Centre in Warszawa, Twarda 51/55, 00-818, Warszawa, Poland.
Institute of Archaeology, Nicolaus Copernicus University in Toruń, Szosa Bydgoska 44/48, 87-100, Toruń, Poland.
Rapid Commun Mass Spectrom. 2019 Aug 30;33(16):1311-1317. doi: 10.1002/rcm.8471.
The trophic enrichment factor (TEF) is a parameter reflecting the difference in isotopic ratio between a consumer's tissues and diet, used in isotopic ecology and paleoecology to track dietary habits. The TEF of sulfur is believed to be low, but was, until now, only documented in a limited number of taxa. In this study we use a subfossil accumulation of bones from a red fox (Vulpes vulpes) den to verify the TEF for sulfur in fox bone collagen.
Collagen was extracted from 30 samples of subfossil bones, including foxes and their prey. The δ S values of the bone collagen samples were measured with an elemental analyzer connected to an isotope ratio mass spectrometer. The TEF was calculated as [Δ S = (mean δ S in predator) - (mean δ S in prey)], using taphonomic indices to estimate the mean diet, and calculated separately for different age classes of the predator.
We modeled 12 variants of TEF for different estimations of the diet composition and for three fox age classes (adult, subadult, and juvenile). The estimated TEF values range from -0.54 to +0.03‰ and are similar to TEFs known for other mammals. Absolute TEF values are nearly equal to or lower than the analytical error, which is ±0.4‰.
For the first time, we present direct δ S data for the bone collagen of a free-living predator and its naturally selected prey. Our results indicate very low or even slightly negative TEF values for sulfur. Furthermore, according to our results, the δ S value should not be considered a reliable indicator of trophic position in terrestrial food webs but rather, it should be used to disentangle different food webs based on different primary producers.
营养富集因子（TEF）是反映消费者组织与食物同位素比率差异的一个参数，在同位素生态学和古生态学中用于追踪饮食习惯。硫的TEF被认为较低，但迄今为止，仅在少数分类群中有记录。在本研究中，我们利用红狐（赤狐）巢穴中的亚化石骨骼堆积物来验证狐骨胶原蛋白中硫的TEF。
从30个亚化石骨骼样本中提取胶原蛋白，这些样本包括狐狸及其猎物。使用连接到同位素比率质谱仪的元素分析仪测量骨胶原蛋白样本的δS值。TEF的计算方法为[ΔS =（捕食者的平均δS）-（猎物的平均δS）]，利用埋藏学指标估计平均食物组成，并针对捕食者的不同年龄组分别计算。
我们针对不同的食物组成估计和三个狐狸年龄组（成年、亚成年和幼年）建立了12种TEF变体模型。估计的TEF值范围为-0.54至+0.03‰，与其他哺乳动物已知的TEF值相似。绝对TEF值几乎等于或低于分析误差±0.4‰。
我们首次展示了自由生活捕食者及其自然选择猎物的骨胶原蛋白的直接δS数据。我们的结果表明硫的TEF值非常低甚至略有负值。此外，根据我们的结果，δS值不应被视为陆地食物网中营养级的可靠指标，而应被用于根据不同的初级生产者来区分不同的食物网。
