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Potapov AM, Tiunov AV, Scheu S. Uncovering trophic positions and food resources of soil animals using bulk natural stable isotope composition. Biol Rev Camb Philos Soc 2019; 94:37-59. [PMID: 29920907 DOI: 10.1111/brv.12434] [Citation(s) in RCA: 70] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2018] [Revised: 05/10/2018] [Accepted: 05/15/2018] [Indexed: 01/24/2023]
Abstract
Despite the major importance of soil biota in nutrient and energy fluxes, interactions in soil food webs are poorly understood. Here we provide an overview of recent advances in uncovering the trophic structure of soil food webs using natural variations in stable isotope ratios. We discuss approaches of application, normalization and interpretation of stable isotope ratios along with methodological pitfalls. Analysis of published data from temperate forest ecosystems is used to outline emerging concepts and perspectives in soil food web research. In contrast to aboveground and aquatic food webs, trophic fractionation at the basal level of detrital food webs is large for carbon and small for nitrogen stable isotopes. Virtually all soil animals are enriched in 13 C as compared to plant litter. This 'detrital shift' likely reflects preferential uptake of 13 C-enriched microbial biomass and underlines the importance of microorganisms, in contrast to dead plant material, as a major food resource for the soil animal community. Soil organic matter is enriched in 15 N and 13 C relative to leaf litter. Decomposers inhabiting mineral soil layers therefore might be enriched in 15 N resulting in overlap in isotope ratios between soil-dwelling detritivores and litter-dwelling predators. By contrast, 13 C content varies little between detritivores in upper litter and in mineral soil, suggesting that they rely on similar basal resources, i.e. little decomposed organic matter. Comparing vertical isotope gradients in animals and in basal resources can be a valuable tool to assess trophic interactions and dynamics of organic matter in soil. As indicated by stable isotope composition, direct feeding on living plant material as well as on mycorrhizal fungi is likely rare among soil invertebrates. Plant carbon is taken up predominantly by saprotrophic microorganisms and channelled to higher trophic levels of the soil food web. However, feeding on photoautotrophic microorganisms and non-vascular plants may play an important role in fuelling soil food webs. The trophic niche of most high-rank animal taxa spans at least two trophic levels, implying the use of a wide range of resources. Therefore, to identify trophic species and links in food webs, low-rank taxonomic identification is required. Despite overlap in feeding strategies, stable isotope composition of the high-rank taxonomic groups reflects differences in trophic level and in the use of basal resources. Different taxonomic groups of predators and decomposers are likely linked to different pools of organic matter in soil, suggesting different functional roles and indicating that trophic niches in soil animal communities are phylogenetically structured. During last two decades studies using stable isotope analysis have elucidated the trophic structure of soil communities, clarified basal food resources of the soil food web and revealed links between above- and belowground ecosystem compartments. Extending the use of stable isotope analysis to a wider range of soil-dwelling organisms, including microfauna, and a larger array of ecosystems provides the perspective of a comprehensive understanding of the structure and functioning of soil food webs.
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Affiliation(s)
- Anton M Potapov
- University of Göttingen, J.F. Blumenbach Institute of Zoology and Anthropology, Untere Karspüle 2, 37073 Göttingen, Germany.,Russian Academy of Sciences, A.N. Severtsov Institute of Ecology and Evolution, Leninsky Prospect 33, 119071 Moscow, Russia
| | - Alexei V Tiunov
- Russian Academy of Sciences, A.N. Severtsov Institute of Ecology and Evolution, Leninsky Prospect 33, 119071 Moscow, Russia
| | - Stefan Scheu
- University of Göttingen, J.F. Blumenbach Institute of Zoology and Anthropology, Untere Karspüle 2, 37073 Göttingen, Germany.,University of Göttingen, Centre of Biodiversity and Sustainable Land Use, Von-Siebold-Str. 8, 37075 Göttingen, Germany
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Resource Utilization by Native and Invasive Earthworms and Their Effects on Soil Carbon and Nitrogen Dynamics in Puerto Rican Soils. FORESTS 2016. [DOI: 10.3390/f7110277] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Melody C, Griffiths B, Dyckmans J, Schmidt O. Stable isotope analysis (δ (13)C and δ (15)N) of soil nematodes from four feeding groups. PeerJ 2016; 4:e2372. [PMID: 27635338 PMCID: PMC5012319 DOI: 10.7717/peerj.2372] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2015] [Accepted: 07/26/2016] [Indexed: 11/23/2022] Open
Abstract
Soil nematode feeding groups are a long-established trophic categorisation largely based on morphology and are used in ecological indices to monitor and analyse the biological state of soils. Stable isotope ratio analysis (13C/12C and 15N/14N, expressed as δ13C and δ15N) has provided verification of, and novel insights into, the feeding ecology of soil animals such as earthworms and mites. However, isotopic studies of soil nematodes have been limited to date as conventional stable isotope ratio analysis needs impractically large numbers of nematodes (up to 1,000) to achieve required minimum sample weights (typically >100 µg C and N). Here, micro-sample near-conventional elemental analysis–isotopic ratio mass spectrometry (μEA–IRMS) of C and N using microgram samples (typically 20 µg dry weight), was employed to compare the trophic position of selected soil nematode taxa from four feeding groups: predators (Anatonchus and Mononchus), bacterial feeders (Plectus and Rhabditis), omnivores (Aporcelaimidae and Qudsianematidae) and plant feeder (Rotylenchus). Free-living nematodes were collected from conventionally and organically managed arable soils. As few as 15 nematodes, for omnivores and predators, were sufficient to reach the 20 µg dry weight target. There was no significant difference in δ15N (p = 0.290) or δ13C (p = 0.706) between conventional and organic agronomic treatments but, within treatments, there was a significant difference in N and C stable isotope ratios between the plant feeder, Rotylenchus (δ15N = 1.08 to 3.22 mUr‰, δ13C = –29.58 to –27.87 mUr) and all other groups. There was an average difference of 9.62 mUr in δ15N between the plant feeder and the predator group (δ15N = 9.89 to 12.79 mUr, δ13C = –27.04 to –25.51 mUr). Isotopic niche widths were calculated as Bayesian derived standard ellipse areas and were smallest for the plant feeder (1.37 mUr2) and the predators (1.73 mUr2), but largest for omnivores (3.83 mUr2). These data may reflect more preferential feeding by the plant feeder and predators, as assumed by classical morphology-based feeding groups, and indicate that omnivory may be more widespread across detritivore groups i.e. bacterial feeders (3.81 mUr2). Trophic information for soil nematodes derived from stable isotope analysis, scaled as finely as species level in some cases, will complement existing indices for soil biological assessment and monitoring, and can potentially be used to identify new trophic interactions in soils. The isotopic technique used here, to compare nematode feeding group members largely confirm their trophic relations based on morphological studies.
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Affiliation(s)
- Carol Melody
- School of Agriculture and Food Science, University College Dublin, Dublin, Ireland; UCD Earth Institute, University College Dublin, Dublin, Ireland
| | - Bryan Griffiths
- Crop and Soil Systems Research, Scotland's Rural College , Edinburgh , United Kingdom
| | - Jens Dyckmans
- Centre for Stable Isotope Research and Analysis, Georg-August Universität Göttingen , Göttingen , Germany
| | - Olaf Schmidt
- School of Agriculture and Food Science, University College Dublin, Dublin, Ireland; UCD Earth Institute, University College Dublin, Dublin, Ireland
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Li X, Xing M, Yang J, Dai X. Earthworm eco-physiological characteristics and quantification of earthworm feeding in vermifiltration system for sewage sludge stabilization using stable isotopic natural abundance. JOURNAL OF HAZARDOUS MATERIALS 2014; 276:353-361. [PMID: 24910912 DOI: 10.1016/j.jhazmat.2014.05.042] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/10/2014] [Revised: 04/15/2014] [Accepted: 05/14/2014] [Indexed: 06/03/2023]
Abstract
Previous studies showed that the presence of earthworm improves treatment performance of vermifilter (VF) for sewage sludge stabilization, but earthworm eco-physiological characteristics and effects in VF were not fully investigated. In this study, earthworm population, enzymatic activity, gut microbial community and stable isotopic abundance were investigated in the VF. Results showed that biomass, average weight, number and alkaline phosphatase activity of the earthworms tended to decrease, while protein content and activities of peroxidase and catalase had an increasing tendency as the VF depth. Earthworm gut microbial communities were dominated by Gammaproteobacteria, and the percentages arrived to 76-92% of the microbial species detected. (15)N and (13)C natural abundance of the earthworms decreased with operation time, and increased as the VF depth. Quantitative analysis using δ(15)N showed that earthworm feeding and earthworm-microorganism interaction were responsible for approximately 21% and 79%, respectively, of the enhanced volatile suspended solid reduction due to the presence of earthworm. The finding provides a quantitative insight into how earthworms influence on sewage sludge stabilization in vermifiltration system.
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Affiliation(s)
- Xiaowei Li
- State Key Laboratory of Pollution Control and Resources Reuse, The National Engineering Research Center for Urban Pollution Control, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, PR China
| | - Meiyan Xing
- State Key Laboratory of Pollution Control and Resources Reuse, The National Engineering Research Center for Urban Pollution Control, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, PR China.
| | - Jian Yang
- State Key Laboratory of Pollution Control and Resources Reuse, The National Engineering Research Center for Urban Pollution Control, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, PR China
| | - Xiaohu Dai
- State Key Laboratory of Pollution Control and Resources Reuse, The National Engineering Research Center for Urban Pollution Control, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, PR China
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Forey E, Barot S, Decaëns T, Langlois E, Laossi KR, Margerie P, Scheu S, Eisenhauer N. Importance of earthworm–seed interactions for the composition and structure of plant communities: A review. ACTA OECOLOGICA-INTERNATIONAL JOURNAL OF ECOLOGY 2011. [DOI: 10.1016/j.actao.2011.03.001] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Christensen H, Fogel ML. Feeding ecology and evidence for amino acid synthesis in the periodical cicada (Magicicada). JOURNAL OF INSECT PHYSIOLOGY 2011; 57:211-219. [PMID: 21075111 DOI: 10.1016/j.jinsphys.2010.11.005] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/09/2009] [Revised: 11/05/2010] [Accepted: 11/06/2010] [Indexed: 05/30/2023]
Abstract
The periodical cicadas of the genus Magicicada (including M. septendecim, M. cassini, and M. septendecula) have the longest juvenile life span of any insect, living underground for 13 or 17 years and feeding exclusively on root xylem fluids. Due to their inaccessible life cycles very little is known about cicada nutrition, despite the fact that members of Magicicada can achieve a very large biomass in woodland habitats east of the Mississippi and hence constitute a major part of the ecosystem where they occur in high densities. Live cicadas were collected at two sites in early June of 2004, during the emergence of Brood X (both M. septendecim and M. cassini were recovered). We used a combination of stable isotopic measurements (δ(15)N and δ(13)C) and multivariate statistical techniques to test for differences in resource acquisition among the cicada species and sexes collected at two locations within the 17-year periodical Brood X range. The amino acid constituents of cicada chitin and organs, plus xylem extracted from a deciduous sapling, were also analyzed. The data show that male and female cicadas have different carbon fractionations, which could reflect differential resource utilization due to oviposition in females. Several essential amino acids for the cicada were absent in xylem. Carbon-isotopic composition of all amino acids in the cicadas was distinctly different from the limited set measured in the xylem. Because of the differences in isotopic composition, we conclude that amino acids were synthesized de novo rather than incorporated directly, most likely produced by endosymbiotic bacteria.
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Affiliation(s)
- Hilary Christensen
- The University of Chicago, Department of the Geophysical Sciences, 5734 S. Ellis Ave., Chicago, IL 60637, USA.
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Nakagawa M, Hyodo F, Nakashizuka T. Effect of forest use on trophic levels of small mammals: an analysis using stable isotopes. CAN J ZOOL 2007. [DOI: 10.1139/z07-026] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The degradation of tropical forests is progressing rapidly and its ecological effects on wild animals are a global concern. We evaluated the hypothesis that small mammals in highly degraded forest occupy higher trophic levels than those in somewhat degraded forests, as indicated by diets high in consumers such as insects, in a tropical rain forest in Sarawak, Malaysia. After correcting for differences in the δ15N values for primary production among the study sites, the δ15Ncorrected values for rats and mice (Muridae) differed significantly among forest types. Rats and mice in more degraded forest had higher δ15Ncorrected values than those in less degraded or primary forest; in contrast, treeshrews (Tupaiidae) and squirrels (Sciuridae) showed no significant differences in the δ15Ncorrected values among forest types. We found significant positive correlations between canopy openness and the δ15Ncorrected values for one species of squirrel and two species of rats. This hypothesis was supported for small mammals that have normal dietary preferences for plants, i.e., omnivorous rodents, but not for those that normally prefer insects, i.e., treeshrews. The δ15N values for omnivorous mammals may be useful as an indicator of changes in food-web structure in response to forest disturbance.
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Affiliation(s)
- Michiko Nakagawa
- Research Institute for Humanity and Nature (RIHN), Kyoto 603-8047, Japan
| | - Fujio Hyodo
- Research Institute for Humanity and Nature (RIHN), Kyoto 603-8047, Japan
| | - Tohru Nakashizuka
- Research Institute for Humanity and Nature (RIHN), Kyoto 603-8047, Japan
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Hendrix PF, Baker GH, Callaham MA, Damoff GA, Fragoso C, González G, James SW, Lachnicht SL, Winsome T, Zou X. Invasion of exotic earthworms into ecosystems inhabited by native earthworms. Biol Invasions 2006. [DOI: 10.1007/s10530-006-9022-8] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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Baugh AT, West AG, Rickart EA, Cerling TE, Ehleringer JR, Dearing MD. STABLE ISOTOPE RATIOS (δ 15N AND δ 13C) OF SYNTOPIC SHREWS (SOREX). SOUTHWEST NAT 2004. [DOI: 10.1894/0038-4909(2004)049<0493:sirnac>2.0.co;2] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Blüthgen N, Gebauer G, Fiedler K. Disentangling a rainforest food web using stable isotopes: dietary diversity in a species-rich ant community. Oecologia 2003; 137:426-35. [PMID: 12898386 DOI: 10.1007/s00442-003-1347-8] [Citation(s) in RCA: 233] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2003] [Accepted: 06/29/2003] [Indexed: 11/28/2022]
Abstract
For diverse communities of omnivorous insects such as ants, the extent of direct consumption of plant-derived resources vs. predation is largely unknown. However, determination of the extent of "herbivory" among ants may be crucial to understand the hyper-dominance of ants in tropical tree crowns, where prey organisms tend to occur scarcely and unpredictably. We therefore examined N and C stable isotope ratios (delta(15)N and delta(13)C) in 50 ant species and associated insects and plants from a tropical rainforest in North Queensland, Australia. Variation between ant species was pronounced (range of species means: 7.1 per thousand in delta(15)N and 6.8 per thousand in delta(13)C). Isotope signatures of the entire ant community overlapped with those of several herbivorous as well as predacious arthropods. Variability in delta(15)N between ants was not correlated with plant delta(15)N from which they were collected. Ant species spread out in a continuum between largely herbivorous and purely predacious taxa, with a high degree of omnivory. Ant species' delta(15)N were consistent with the trophic level predicted by natural feeding observations, but not their delta(13)C. Low delta(15)N levels were recorded for ant species that commonly forage for nectar on understorey or canopy plants, intermediate levels for species with large colonies that were highly abundant on nectar and honeydew sources and were predacious, and the highest levels for predominantly predatory ground-foraging species. Colonies of the dominant weaver-ants (Oecophylla smaragdina) had significantly lower delta(15)N in mature forests (where preferred honeydew and nectar sources are abundant) than in open secondary vegetation. N concentration of ant dry mass showed only very limited variability across species and no correlation with trophic levels. This study demonstrates that stable isotopes provide a powerful tool for quantitative analyses of trophic niche partitioning and plasticity in complex and diverse tropical omnivore communities.
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Affiliation(s)
- Nico Blüthgen
- Department of Animal Ecology I, University of Bayreuth, 95440, Bayreuth, Germany.
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Tayasu I, Nakamura T, Oda H, Hyodo F, Takematsu Y, Abe T. Termite ecology in a dry evergreen forest in Thailand in terms of stable (δ13C andδ15N) and radio (14C,137Cs and210Pb) isotopes. Ecol Res 2002. [DOI: 10.1046/j.1440-1703.2002.00479.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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