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Compound‐specific isotope analysis of amino acids as a new tool to uncover trophic chains in soil food webs
Ecological Monographs ( IF 6.1 ) Pub Date : 2019-07-09 , DOI: 10.1002/ecm.1384
Melanie M. Pollierer 1 , Thomas Larsen 2 , Anton Potapov 1, 3 , Adrian Brückner 4 , Michael Heethoff 4 , Jens Dyckmans 5 , Stefan Scheu 1, 6
Affiliation  

Food webs in soil differ fundamentally from those aboveground; they are based on inputs from both living plants via root exudates, and from detritus, which is a complex mixture of fungi, bacteria, and dead plant remains. Trophic relationships are difficult to disentangle due to the cryptic lifestyle of soil animals and inevitable microbial contributions to their diet. Compound‐specific isotope analysis of amino acids (AAs) is increasingly used to explore complex food webs. The combined use of AA δ13C and δ15N values is a promising new approach to disentangle trophic relationships since it provides independent but complementary information on basal resources, as well as the trophic position of consumers. We conducted a controlled feeding study in which we reconstructed trophic chains from main basal resources (bacteria, fungi, plants) to primary consumers (springtails, oribatid mites) and predators (gamasid mites, spiders). We analyzed dual compound‐specific isotope AA values of both resources and consumers. By applying an approach termed “stable isotope (13C) fingerprinting” we identified basal resources, and concomitantly calculated trophic positions using 15N values of trophic and source AAs in consumers. In the 13C fingerprinting analysis, consumers in general grouped close to their basal resources. However, higher than usual offsets in AA δ13C between diet and consumers suggest either gut microbial supplementation or the utilization of specific resource fractions. Identification of trophic position crucially depends on correct estimates of the trophic discrimination factor (TDFGlu‐Phe), which was close to the commonly applied value of 7.6‰ in primary consumers feeding on microbial resources, but considerably lower in arachnid predators (~2.4‰), presumably due to higher diet quality, excretion of guanine, and fluid feeding. While our feeding study demonstrates that dual compound‐specific AA analyses hold great promise in delineating trophic linkages among soil‐dwelling consumers and their resources, it also highlights that a “one‐size‐fits‐all” approach to TDFGlu‐Phe does not apply to soil food webs.

中文翻译:

氨基酸的化合物特异性同位素分析是揭示土壤食物网中营养链的新工具

土壤中的食物网与地上的食物网根本不同。它们是基于两种植物通过根系分泌物以及碎屑的输入,碎屑是真菌,细菌和死植物残渣的复杂混合物。由于土壤动物的神秘生活方式和微生物对饮食的必然贡献,营养关系很难解开。氨基酸(AAs)的化合物特异性同位素分析越来越多地用于探索复杂的食物网。的组合使用AA的δ 13 C和δ 15N值是解决营养关系的一种有前途的新方法,因为它提供了有关基础资源以及消费者营养位置的独立但互补的信息。我们进行了一项有控制的喂养研究,在该研究中,我们从主要基础资源(细菌,真菌,植物)到主要消费者(跳蚤、,螨,蜘蛛)和食肉动物(gamasid螨,蜘蛛)重建了营养链。我们分析了资源和消费者的双重化合物特定同位素AA值。通过应用一种称为“稳定同位素(13 C)指纹”的方法,我们确定了基础资源,并使用15 N的营养级和源AA值在消费者中计算了营养级。在13C指纹分析表明,消费者通常将其基本资源分组在一起。然而,比在AA通常偏移更高δ 13饮食和消费者℃之间建议要么肠道微生物补充或特定资源馏分的利用率。营养位置的确定主要取决于营养歧视因素的正确估计(TDF Glu-Phe),接近于以微生物资源为食的主要消费者的普遍使用价值7.6‰,但在蜘蛛食肉动物中则低得多(〜2.4‰),这可能是由于较高的饮食质量,鸟嘌呤排泄和液体喂养所致。尽管我们的喂养研究表明,双重化合物特有的AA分析在描述土壤住户消费者及其资源之间的营养联系方面具有广阔的前景,但同时也强调了TDF Glu-Phe的“千篇一律”方法并没有适用于土壤食物网。
更新日期:2019-07-09
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