FIGURE 5.

Simulations with an interaction-free null model. Evenness does not alter PEP in simulations, though the variance of PEP increases for low evenness, when most taxa are absent across all samples (A). When introducing group structure, PEP varies non-linearly with group number (B). Count matrices were simulated with 50 taxa and 10 samples (A) and 120 taxa and 60 samples (B) and networks were built using Spearman with cut-off at ±0.2. For the cyan box plots, significance was assessed by computing p-values from permutation and bootstrap distributions and correcting for multiple testing with Benjamini and Hochberg’s (1995) procedure. Matrix generation and network construction were repeated 100 times for each box plot (10 times when significance was assessed). Permutations and bootstraps were carried out with 100 iterations each. The parameter “minocc” refers to a filter step that removes all taxa occurring in less than the specified sample number.