Microbial generalists and specialists differently contribute to the community diversity in farmland soils

INTRODUCTION: Microbial generalists and specialists are thought to have distinct impacts on community dynamics, while there have been limited efforts to estimate their contribution to microbial diversity. OBJECTIVES: We aimed to resolve this research gap in microbial ecology to strengthen our understanding of the biogeography of microbial diversity, with implications for global-scale biodiversity mapping. METHODS: Herein, we identified the ecological characteristics of microbial generalists and specialists across over 3,000 farmland soil samples from eleven countries that encompassed seven climate types. RESULTS: Considering the distinct distributions of generalists and specialists in degree of connexions, betweenness and as key species in network topology, both generalists and specialists contributed to species interactions, though through different modalities. A stronger signature of deterministic processes in specialists indicated their lower tolerance to environment fluctuations. Generalists, in contrast, were more characterized by stochastic processes with higher diversification and transition rates that suggested more important roles in maintaining community stability when exposed to environmental disturbances. The relationship between latitude and diversity combining with distance-decay effects showed that generalists dampened microbial biogeographical patterns, with contrasting impacts by specialists. CONCLUSION: By demonstrating the ecological characteristics of microbial generalists and specialists, this study deepens our understanding of microbial diversity and highlights the need to impart systematic distinctions among different categories of species when modelling and predicting the fate of ecosystems in the face of global climate change, rather than assuming that species are functionally equivalent.