Fig. 1.

The composition of microbial communities in farmland soils and the definition of generalist and specialist groups. (a) The distribution of communities at phylum level. The assigned species were further classified into generalist, specialist and opportunist groups. The richness and relative abundance composition of different groups were provided. (b) Classification of generalists and specialists. By comparing the expected and observed distribution, species observed in one environment and more than five environments were defined as specialists and generalists, respectively. The remaining were opportunists. The niche breadth, which indicates the occurrence frequency of species, and the relative abundance of the specialists and generalists are shown. Relative abundance is shown on a logarithmic (lg) scale on the x axis. (c) Taxonomic distribution of generalists and specialists at the phylum level, based on richness (left) and relative abundance (right). The thickness of each ribbon (i.e., the links in the middle area) in the circos-plot represents the richness or relative abundance of generalist and specialist groups assigned to different phyla. (d) Phylogenetic tree of the most abundant generalists and specialists (i.e., taxa with top 15 relative abundance in generalist and specialist groups) with their occurrence in different samples. Red and grey represents the existence and absence of species, respectively. The sample climate type, taxonomic information and species ecotypes are indicated by different colours.