Phylogenetic relatedness enhances the understanding of soil microbial coexistence in alpine wetlands of the Tibetan Plateau

Soil microorganisms, spanning diverse phylogenetic lineages, form complex ecological networks wherein various species coexist and contribute to multiple ecosystem services. While microbial networks facilitate the understanding of their coexistence and functions in soils, the influence of phylogenetic relatedness among soil microbes themselves on these networks remains largely unknown. To address this knowledge gap, we conducted a comprehensive survey of soil bacteria and archaea in twenty alpine wetlands on the Tibetan Plateau, characterized by wide edaphic and climatic heterogeneity. Through network and phylogenetic analyses, we evaluated the complexity of network associations and their dependence on phylogenetic relatedness. Our findings revealed consistencies and discrepancies between phylogenetic relatedness and network associations within soil bacterial and archaeal communities. Specifically, in bacterial networks, both positive and negative complexity were significantly associated with mean phylogenetic distance, whereas in archaeal networks, only negative complexity correlated with mean phylogenetic distance. Even after accounting for the effects of environmental factors, we observed that phylogenetic relatedness still explained variations in the complexities of bacterial and archaeal associations. Furthermore, a multi-threshold analysis indicated that network complexity exhibited phylogenetic signals in both bacterial and archaeal networks, albeit within different associated distance classes, suggesting distinct coexistence mechanisms of soil bacteria and archaea driven by niche and fitness trade-offs. Overall, our findings underscore the importance of incorporating phylogenetic information when studying microbial communities in complex soil habitats and demonstrate that phylogenetic relatedness crucially shapes coexistence outcomes among soil microbes.