Contrasting responses of diazotrophic specialists, opportunists, and generalists to steppe types in Inner Mongolia

Assembly mechanisms and responses of diazotrophic habitat specialists, opportunists, and generalists may differ among various steppe ecosystems. In this study, we investigated the ecological processes that determine the assemblies of diazotrophic communities in meadows and typical steppes (MT), desert steppes (D), and sandy steppes (S) and the effects of habitat environments on diazotrophic specialists, opportunists, and generalists in Inner Mongolia, China. The results showed that taxonomic and phylogenetic communities of diazotrophs were clustered according to their habitat types, as community dissimilarities among habitat types were significantly higher than those within them. Variable selection and dispersal limitation were recognized as the dominant ecological processes that shape diazotrophic community assemblages. Furthermore, the diazotrophic populations were dichotomized into specialists, opportunists and generalists with various strategies to adapt to habitat types. The richness of specialists significantly correlated with vegetation variables, implying that specialists have greater responses to vegetation than generalists and opportunists. This study provides insights into the mechanisms of diazotrophic community differentiation when habitat environments change.