We developed a random graph null model to compare the statistics of G2 to randomized versions of the same species-species network. The procedure generates 10,000 randomized configurations of G2, under the condition that the degrees are fixed but connections are randomized. Subsequently, the cci and bci are applied to these randomized networks to determine the range of values that these measures can take (Supplementary Information, S3.2). In other words, we provide a negative control for the measures applied on G2 (a so-called null hypothesis). In this way, we can identify which nodes show features that may be used to characterize the trypsin oscillator.