Fig. 5: The microbiome biogeography across a 2,500-km transect.

a The terrain profile of China along 36 degrees north latitude to show the ladder-like topography. The microbial species profiles become less similar between samples in the same water ecosystem, as the distance (b) and altitude (c) difference increase. Spearman’s rank correlation coefficient (R) and statistical significance (P) are calculated. d The abundance variation of two phyla in the river samples from across a 2500-km transect (Ladder 1, n = 108; Ladder 2, n = 40; Ladder 3, n = 24). Each dot represents the relative abundance (log₁₀) of the phylum of each sample, produced by the MetaPhlAn (version 4.0.1)³⁷. The statistical significance of the abundance differences between steps of the ladder is calculated by the two-sided Mann–Whitney–Wilcoxon test. Boxes represent the interquartile range between the first and third quartiles and the line inside represents the median. Whiskers denote the lowest and highest values within the 1.5× interquartile range from the first and third quartiles, respectively. The number of the shared genes decreases between samples in the same water ecosystem, as the distance (e) and altitude (f) difference increase. Spearman’s rank correlation coefficient (R) and statistical significance (P) are calculated. In all scatter plots, each dot represents a pairwise comparison in 1) microbial similarity quantified by the Bray–Curtis distance of species profiles produced by MetaPhlAn (version 4.0.1)³⁷; 2) shared gene count; 3) geographical distance; and 4) altitude, which are conducted on samples within the Tibetan Plateau, as well as between the Tibetan Plateau and the others.