Functional redundancy across space and time in litter-degrading fungal communities

Abstract

Introduction

Microbial-driven litter decomposition contributes significantly to global carbon (C) turnover. Fungi play central roles in the degradation process due to their ability to hydrolyse recalcitrant litter components. The spatiotemporal variations in taxonomic composition of litter-degrading fungi have been well documented. However, associated variations in litter-degradation-related functional composition of fungal communities remain unexplored.

Materials and Methods

In this study, a 16-week field-based buried rice straw experiment was conducted at three experimental sites across subtropical China in combination with laboratory ¹³C-straw-based DNA stable-isotope probing (DNA-SIP) microcosm experiments. Amplicon sequencing combined with shotgun metagenomic sequencing were the approaches of choice.

Results

The field experiment showed that the taxonomic composition of the straw-degrading fungal community was highly variable while the functional composition was rather stable. The higher permutational multivariate analysis of variation F scores (20.904−48.660) and the steeper slopes (1.92 E-04−4.15E-04) of the distance decay relationship for taxonomic composition than for function across periods (with lower F scores = 7.047−21.601 and gradual slopes = −1.33 E-05 to −1.03E-04) both indicated that the spatiotemporal patterns of functional composition in litter-degrading fungi community were more conserved. The laboratory DNA-SIP confirmed the field observations and showed that the conserved functional composition in litter-degrading fungi was underpinned by a high functional redundancy of Basidiomycota.

Conclusion

Function and taxonomy of litter-degrading fungi were decoupled. The functional composition of the litter-degrading fungal community was highly conserved in space and time, the taxonomic composition less so. The main drivers behind the observed taxonomic decoupling are probably/most likely functional redundancy and metabolic niche selection resulting in conservation of function, with changing environmental conditions and dispersal limitation drove the observed high taxonomic turnover of the community over the course of the litter degradation progression. Our study provides valuable insights in the ecology of fungi and their roles in in global C sequestration for ecosystem sustainable development.