Stable Isotope Analysis in R - package
The mixing model component of SIAR uses Bayesian Inference to solve for the most likely set of dietary proportions given the isotopic ratios in a set of possible food sources and a set of consumers. The model is similar in principle to IsoSource (Phillips & Gregg 2003) but allows all sources of uncertainty such as in the sources or trophic fractionation values to be propagated through the model to return a true probability distribution of estimated dietary proportions. Previously it was necessary to ignore variation and uncertainty and work only with mean estimates of isotope ratios.
Additionally, SIAR will take account of a grouping structure and directly compare the estimated diets between groups of individuals. These groups could represent multiple observations on the same individual, sub-populations or entire species.
Parnell, A.C., Inger R., Bearhop, S. & Jackson, A.L. 2010. Source partioning using stable isotopes: coping with too much variation. PLoS ONE, 5(3), e9672.