Marine Ecology Progress Series
MEPS is a leading hybrid research journal on all aspects of marine, coastal and estuarine ecology. Priority is given to outstanding research that advances our ecological understanding.
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DOI: https://doi.org/10.3354/meps10535
copiedStatistical basis and outputs of stable isotope mixing models: Comment on Fry (2013)
- Brice X. Semmens
- Eric J. Ward
- Andrew C. Parnell
- Donald L. Phillips
- Stuart Bearhop
- Richard Inger
- Andrew Jackson
- Jonathan W. Moore
ABSTRACT: Fry (2013; Mar Ecol Prog Ser 472:1–13) reviewed approaches to solving underdetermined stable isotope mixing systems, and presented a novel approach based on graphical summaries. He inaccurately characterized the statistics and interpretation of outputs from IsoSource and more recent Bayesian mixing model tools (e.g. SIAR, MixSIR), however, and as an alternative promoted an approach—not based on likelihood methods—that uses graphing and 2 new metrics for tracking source contributions to a mixture. Fry’s approach does not provide statistical probability densities associated with source contribution parameter estimates, has little applicability to complex mixing systems such as hierarchical models, and relies on the subjective interpretation of graphing products. We clarify the analytic theory underlying common mixing model approaches and provide an analysis of the 4-source, 2-tracer underdetermined mixing system example in Fry (2013), using both a Bayesian mixing model and Fry’s graphical analysis and summary metrics. We demonstrate that properly interpreted Bayesian approaches yield distributions of parameter estimates that can reflect multi-modality, covariance and parameter uncertainty.
KEYWORDS
Brice X. Semmens (Co-author)
- Scripps Institution of Oceanography, University of California San Diego, 9500 Gilman Drive, La Jolla, California 92039-0202, USA
Eric J. Ward (Co-author)
- Conservation Biology Division, Northwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, 2725 Montlake Blvd. East, Seattle, Washington 98112, USA
Andrew C. Parnell (Co-author)
- School of Mathematical Sciences (Statistics), Complex and Adaptive Systems Laboratory, University College Dublin, Ireland
Donald L. Phillips (Co-author)
- U.S. Environmental Protection Agency, National Health and Environmental Effects Research Laboratory, Western Ecology Division, 200 SW 35th St., Corvallis, Oregon 97333, USA
Stuart Bearhop (Co-author)
- Centre for Ecology and Conservation, School of Biosciences, University of Exeter, Exeter EX4 4SB, UK
Richard Inger (Co-author)
- Environment and Sustainability Institute, School of Biosciences, University of Exeter, Exeter EX4 4SB, UK
Andrew Jackson (Co-author)
- Department of Zoology, School of Natural Sciences, and Centre for Biodiversity Research, Trinity College Dublin, Dublin 2, Ireland
Jonathan W. Moore (Co-author)
- Earth to Ocean Research Group, Simon Fraser University, 8888 University Drive, Burnaby, British Columbia V5A 1S6, Canada