Fig. 2

Diversity and principal component analysis of microbial communities. (A) Shannon index calculated using the Kruskal–Wallis H test; larger Shannon values indicate higher community diversity. (B) Simpson index calculated using the Kruskal–Wallis H test; the greater the value of Simpson’s index, the lower the diversity of the community. (C) Richness and evenness of species within the samples: Species richness is indicated by the width of the curve along the horizontal axis—the wider the curve (greater horizontal spread), the more diverse the species composition. The evenness of the species composition is reflected by the shape of the curve—the flatter the curve (smaller vertical spread), the higher the evenness. (D) Principal Component Analysis (PCA): By decomposing variances, PCA displays the differences among multiple datasets on a coordinate plot. Axes represent the principal components with the largest variance. The closer the clustering of points within the same group, the better the stability within that group. The greater the distance between different groups, the larger the differences between them.