Compound‐specific isotope analysis of amino acids as a new tool to uncover trophic chains in soil food webs
Compound‐specific isotope analysis of amino acids as a new tool to uncover trophic chains in soil food webs
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DOI：
10.1002/ecm.1384
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发表时间：
2019-07
影响因子：
6.1
通讯作者：
Melanie M. Pollierer;T. Larsen;A. Potapov;A. Brückner;M. Heethoff;J. Dyckmans;S. Scheu
中科院分区：
文献类型：
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作者：
Melanie M. Pollierer;T. Larsen;A. Potapov;A. Brückner;M. Heethoff;J. Dyckmans;S. Scheu
土壤中的食物网与地上的食物网有根本的不同；它们是基于两种活植物通过根分泌物和碎屑的输入，碎屑是真菌、细菌和死亡植物遗骸的复杂混合物。由于土壤动物神秘的生活方式和不可避免的微生物对其饮食的贡献，营养关系很难解开。氨基酸的化合物特异性同位素分析(AAs)越来越多地被用于探索复杂的食物网。结合使用AAδ^(13)C和δ^(15)N值是一种很有前途的新方法，因为它提供了关于基础资源和消费者营养位置的独立但互补的信息。我们进行了一项控制饲养研究，重建了从主要基础资源(细菌、真菌、植物)到初级消费者(跳虫、甲螨)和捕食者(革螨、蜘蛛)的营养链。我们分析了资源和消费者的双重化合物特定同位素AA值。通过一种名为“稳定同位素(^(13)C)指纹”的方法，我们确定了基础资源，并利用消费者体内营养和来源AA的^(15)N值计算了营养位置。在^(13)C指纹分析中，消费者通常将他们的基本资源归类为接近他们的群体。然而，饮食和消费者之间AAδ^(13)C的偏移量高于正常水平，表明要么是肠道微生物补充剂，要么是对特定资源部分的利用。营养位置的确定关键取决于对营养鉴别因子(TDFGlu-Phe)的正确估计，在以微生物资源为食的初级消费者中，TDFGlu-Phe接近7.6Phe的普遍应用值，但在蜘蛛类捕食者中(~2.4Phe)，TDFGlu-Phe的应用值要低得多，这可能是由于较高的饮食质量、鸟嘌呤的排泄和液体摄食。虽然我们的喂养研究表明，双重化合物特定的AA分析在描绘土壤消费者及其资源之间的营养联系方面具有很大的前景，但它也强调了TDF_(Glu-Phe)的“一刀切”方法不适用于土壤食物网。
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 δ^(13)C and δ^(15)N 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 (^(13)C) fingerprinting” we identified basal resources, and concomitantly calculated trophic positions using ^(15)N values of trophic and source AAs in consumers. In the ^(13)C fingerprinting analysis, consumers in general grouped close to their basal resources. However, higher than usual offsets in AA δ^(13)C 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 (TDF_(Glu‐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 TDF_(Glu‐Phe) does not apply to soil food webs.