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Laboratory measures of isotope discrimination factors: comments on
Article first published online: 29 JUN 2010
DOI: 10.1111/j.1365-2664.2009.01730.x
© 2010 The Authors. Journal compilation © 2010 British Ecological Society
Additional Information
How to Cite
Perga, M.-E. and Grey, J. (2010), Laboratory measures of isotope discrimination factors: comments on . Journal of Applied Ecology, 47: 942–947. doi: 10.1111/j.1365-2664.2009.01730.x
Publication History
- Issue published online: 29 JUN 2010
- Article first published online: 29 JUN 2010
- Received 4 May 2009; accepted 8 October 2009 Handling Editor: Morten Frederiksen
Keywords:
- dietary protein source;
- food web;
- isotope routing;
- nutrient allocation;
- omnivorous;
- stable isotope analysis
Summary
1. In a recent paper, Caut, Angulo & Courchamp (2008, Functional Ecology, 22, 255) experimentally measured isotope discrimination factors for rats Rattus rattus. In their study, values for their discrimination factors spanned a much larger range than previously reported in the literature and were found to be negatively related to the stable isotope composition of the diet that the rats were fed.
2. In a subsequent meta-analysis, Caut, Angulo & Courchamp (2009, Journal of Applied Ecology, 46, 443) confirmed the trends they had found in their previous study and pointed to a method for obtaining adequate values for discrimination factors when they could not be measured experimentally.
3.Synthesis and applications. We argue that the discrimination factors determined by Caut et al. (2008) were an artefact of experimental design. We also argue that the reported linear relationships between the stable isotope composition of the diet and isotope discrimination factors in their follow-up meta-analyses (Caut et al. 2009) do not reflect relevant trends that can be extrapolated to the field and that the method they proposed for obtaining adequate values for discrimination factors should be used with considerable care.