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Compound-specific isotope analysis of amino acids as a new tool to uncover trophic chains in soil food webs

Pollierer, Melanie M. and Larsen, Thomas and Potapov, Anton and Brückner, Adrian and Heethoff, Michael and Dyckmans, Jens and Scheu, Stefan (2019) Compound-specific isotope analysis of amino acids as a new tool to uncover trophic chains in soil food webs. Ecological Monographs, 89 (4). Art. No. e01384. ISSN 0012-9615. https://resolver.caltech.edu/CaltechAUTHORS:20190823-082659774

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Abstract

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.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1002/ecm.1384DOIArticle
ORCID:
AuthorORCID
Brückner, Adrian0000-0002-9184-8562
Heethoff, Michael0000-0003-3453-4871
Additional Information:© 2019 by the Ecological Society of America. Issue Online: 01 November 2019; Version of Record online: 09 July 2019; Accepted manuscript online: 12 June 2019; Manuscript accepted: 02 May 2019; Manuscript revised: 08 April 2019; Manuscript received: 07 December 2018.
Subject Keywords:13C fingerprinting; Araneae; Collembola; compound‐specific analysis; Gamasina; Oribatida; stable isotopes; trophic discrimination factor; trophic fractionation; δ13C; δ15N
Issue or Number:4
Record Number:CaltechAUTHORS:20190823-082659774
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20190823-082659774
Official Citation:Pollierer, M. M., Larsen, T., Potapov, A., Brückner, A., Heethoff, M., Dyckmans, J., and Scheu, S. 2019. Compound‐specific isotope analysis of amino acids as a new tool to uncover trophic chains in soil food webs. Ecological Monographs 89(4):e01384. 10.1002/ecm.1384
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:98144
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:23 Aug 2019 15:37
Last Modified:25 Jun 2020 17:17

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