Fig. 5

Principal component analysis (PCA) biplots of (a) gene abundances and (b) the gene proportions in the total prokaryotic abundances in different ecosystems as the groups. The x and y axes represent the first two principal components (PCs), capturing the most significant variation in the data. The length of vectors represents the importance of that gene in explaining the variance captured by the PCs. The ellipses in different colors represent the distribution of samples from different ecosystems (95% confidence intervals).