Extended Data Fig. 4: Variability in daily abundance changes for human gut microbiota.

a-d, Black data points show the standard deviation of daily OTU abundance changes as a function of average daily OTU abundances \(x_m = \frac{1}{2}\left[ {\log \left( {X_k(t + 1)} \right) + {\mathrm{log}}(X_k(t))} \right]\) in humans. Gray data points were generated by simulating time series data in which OTU abundance changes originated exclusively from Poissonian sampling noise. The simulations were performed by sampling sequencing read counts from the underlying OTU abundance distributions empirically observed in humans A, B, M3, and F4 (Methods). Random zero counts were added for each OTU to match the frequency of its zero counts in the real data. Sequencing reads were sampled to the same depths as in the real data. The simulations demonstrate that the observed decrease in the variability of OTU abundance changes as a function of the average daily OTU abundances is not a result of simple Poissonian sampling effects.