Supplement 1. R source code for a two-source simulation mixing model that detects 15N-enriched seed in seed batches composed of unknown quantities of 15N-enriched (marked) and normal (unmarked) seeds.

File List Isotope_mix.R (md5: 1ad414fab0125136b63280ca539c8e3e) – R source code for two-source mixing model<br> datos.csv (md5: 9c6bd3134e2b86bb3b2db0b129ceb1a5) – data file containing of ¹⁵N atom % values and number of seeds per batch Description File contains the R source code Isotope_mix.R, a program to estimate the number of marked (¹⁵N- enriched) and unmarked (i.e., normal) seeds in a batch of n seeds. The program looks for the combination of marked and unmarked seeds that maximized the likelihood of observing a value of ¹⁵N atom % similar to the observed one. The empirical distributions of ¹⁵N from a particular combination of marked and unmarked seeds were estimated by simulating 10⁶ (a million) such seed mixtures by sampling from the combinations of Gaussian distribution fitted to the positive and negative controls (with truncation for the marked ones). Confidence intervals were found by looking at those combinations of marked and un-marked seeds that where 2 likelihood units from the maximum.