Lower functional redundancy in “narrow” than “broad” functions in global soil metagenomics
Abstract. Understanding the relationship between soil microbial taxonomic compositions and functional profiles is essential for predicting ecosystem functions under various environmental disturbances. However, even though microbial communities are sensitive to disturbance, ecosystem functions remain relatively stable, as soil microbes are likely to be functionally redundant. Microbial functional redundancy may be more associated with “broad” functions carried out by a wide range of microbes, than with “narrow” functions specialized by specific microorganisms. Thus, a comprehensive study to evaluate how microbial taxonomic compositions correlate with “broad” and “narrow” functional profiles is necessary. Here, we evaluated soil metagenomes worldwide to assess whether functional and taxonomic diversities differ significantly between the five “broad” and the five “narrow” functions that we chose. Our results revealed that compared with the five “broad” functions, soil microbes capable of performing the five “narrow” functions were more taxonomically diverse, and thus their functional diversity was more dependent on taxonomic diversity, implying lower levels of functional redundancy in “narrow” functions. Co-occurrence networks indicated that microorganisms conducting “broad” functions were positively related, but microbes specializing “narrow” functions were interacting mostly negatively. Our study provides strong evidence to support our hypothesis that functional redundancy is significantly different between “broad” and “narrow” functions in soil microbes, as the association of functional diversity with taxonomy were greater in the five “narrow” rather than the five “broad” functions.