Stable C and N isotope ratios reveal soil food web structure and identify the nematode Eudorylaimus antarcticus as an omnivore–predator in Taylor Valley, Antarctica
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Soil food webs of the McMurdo Dry Valleys, Antarctica are simple. These include primary trophic levels of mosses, algae, cyanobacteria, bacteria, archaea, and fungi, and their protozoan and metazoan consumers (including relatively few species of nematodes, tardigrades, rotifers, and microarthropods). These biota are patchily distributed across the landscape, with greatest faunal biodiversity associated with wet soil. Understanding trophic structure is critical to studies of biotic interactions and distribution; yet, McMurdo Dry Valley soil food web structure has been inferred from limited laboratory culturing and microscopic observations. To address this, we measured stable isotope natural abundance ratios of C (13C/12C) and N (15N/14N) for different metazoan taxa (using whole body biomass) to determine soil food web structure in Taylor Valley, Antarctica. Nitrogen isotopes were most useful in differentiating trophic levels because they fractionated predictably at higher trophic levels. Using 15N/14N, we found that three trophic levels were present in wet soil habitats. While cyanobacterial mats were the primary trophic level, the nematode Plectus murrayi, tardigrade Acutuncus antarcticus, and rotifers composed a secondary trophic level of grazers. Eudorylaimus antarcticus had a 15N/14N ratio that was 2–4‰ higher than that of grazers, indicating that this species is the sole member of a tertiary trophic level. Understanding the trophic positions of soil fauna is critical to predictions of current and future species interactions and their distributions for the McMurdo Dry Valleys, Antarctica.
KeywordsDry Valleys Predator Trophic levels Isotopic fractionation Feeding ecology Connectivity
This work was funded by the United States National Science Foundation (NSF), McMurdo Dry Valleys Long Term Ecological Research (MCM LTER) site, PLR 1115245. Geospatial support for this work was provided by the Polar Geospatial Center under NSF OPP awards 1043681 & 1559691. We are grateful to many people who helped with this work, especially the McMurdo Dry Valleys LTER group. Matthew Knox helped collect samples in the field. Members of the Wall Lab at Colorado State University, in particular Amber Cavin, Cecilia Milano de Tomasel, and Emily Bernier, helped with lab work. Thanks also to the Crary Laboratory staff, Stable Isotope Mass Spectrometry Laboratory at Kansas State University, and PHI helicopters whose assistance with lab and fieldwork helped make this work possible.
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Conflict of interest
The authors declare that they have no conflict of interest.
- Ayres E, Wall DH, Adams BJ, Barrett JE, Virginia RA (2007) Unique similarity of faunal communities across aquatic–terrestrial interfaces in a polar desert ecosystem: soil–sediment boundaries and faunal community. Ecosystems 10:523–535. https://doi.org/10.1007/sl0021-007-9035-x CrossRefGoogle Scholar
- Campbell IB, Claridge GC, Campbell DI, Balks MR (1998) The soil environment of the McMurdo Dry Valleys, Antarctica. In: Priscu JC (ed) Ecosystem dynamics in a polar desert: the McMurdo Dry Valleys, Antarctica. American Geophysical Union, Washington DC, pp 297–322Google Scholar
- Gooseff MN, Barrett JE, Adams BJ, Doran PT, Fountain AG, Lyons WB, McKnight DM, Priscu JC, Sokol SR, Takacs-Vesbach C, Vandegehuchte ML, Virginia RA, Wall DH (2017b) Decadal ecosystem response to an anomalous melt season in a polar desert in Antarctica. Nat Ecol Evol 1:1334–1338. https://doi.org/10.1038/s41559-017-0253-0 CrossRefPubMedGoogle Scholar
- Hollis JP (1957) Cultural studies with Dorylaimus ettersbergensis. Phytopathology 47:468–473Google Scholar
- Hooper DJ (1970) Extraction of free-living stages from soil. In: Southey JF (ed) Laboratory methods for work with plant and soil nematodes, 6th edn. Ministery of Agriculture, Fisheries and Food, London, pp 5–30Google Scholar
- Spaulding SA, McKnight DM (1998) Diatoms as indicators of environmental change in antarctic freshwaters. In: Smol J, Stoermer EF (eds) The diatoms: applications for the environmental and earth sciences. Cambridge University Press, Cambridge, pp 249–263Google Scholar
- Tjepkema J, Ferris V, Ferris J (1971) Review of the Genus Aporcelaimellus Heyns, 1965 and Six Species Groups of the Genus Eudorylaimus Andrassy, 1959 (Nematoda: Dorylaimida). Purdue University Agricultural Research Bulletin, 882, West LafayetteGoogle Scholar
- Van Horn DJ, Wolf CR, Colman DR, Jiang X, Kohler TJ, McKnight DM, Stanish LF, Yazzie T, Takacs-Vesbach CD (2016) Patterns of bacterial biodiversity in the glacial meltwater streams of the McMurdo Dry Valleys, Antarctica. FEMS Microbiol Ecol 92:1–16. https://doi.org/10.1093/femsec/fiw148 Google Scholar