Stable Isotope Mixing Polygon Simulation
Smith, J.A., D. Mazumder, I. M. Suthers, M. D. Taylor (2013) To fit or not to fit: evaluating stable isotope mixing models using simulated mixing polygons. Methods in Ecology and Evolution 4 612-618, DOI: 10.1111/2041-210X.12048
UPDATE: Version 1.2 released of MixPolySim_2iso_1.2. See downloads below.
This simulation is used to evaluate stable isotopic mixing models that incorporate uncertainty in dietary source data and in trophic enrichment factors (e.g. SIAR ). The simulation should be used before the mixing model, to determine if each consumer can actually be explained by that model.
A consumer will either be inside 5% or more of the simulated mixing polygons (and can logically be included in the analysis), or will be inside fewer than 5% of mixing polygons (and must be excluded from the mixing model). In the latter case, some decisions must be made before the mixing model is calculated (using SIAR, for example).
The mixing polygon simulation has been made available in both R and MATLAB environments. The scripts are available for download below. The simulation can be used for studies using two isotopes (e.g. C13 and N15), or three isotopes (e.g. C13, N15, S34), which require different scripts. These scripts were made available as supplementary information to the Methods in Ecology and Evolution article, but the scripts available below are the most recent versions.
For simulation details and a discussion of model evaluation see the article by Smith et al. (2013) . For practical advice on running the scripts read Instructions. For further information, contact James Smith.
R script for 2 isotopes (Version 1.0)