FIGURE 3.

Log‐ratio PCA and diagnostics (columns) for the real data examples. The first column (a and d) displays the observations on the 1st and 2nd principal axes, and colours indicate treatment groups. The second column (b and e) displays the correlation between S (transformed abundances) and $\mathrm{r}$. The third column (c and f) displays the log contribution to the 1st axis per taxon versus its log mean abundance. The negative correlations and the relatively high and similar contributions amongst the low abundance taxa suggest there is an issue with row centring (and thus with log‐ratio PCA) for both data examples