Microbial phylogenetic relatedness links to distinct successional patterns of bacterial and fungal communities

Abstract

Development of soil microbial communities along ecological succession is crucial for ecosystem functioning and maintenance. However, ecological processes mediating microbial community assembly and microbial co-occurrence patterns along ecological succession remain unclear. Here, we explored community phylogenetic structures, ecological processes driving community phylogenetic turnover, and taxa co-occurrence patterns in bacterial and fungal communities across a well-established chronosequence of post-mining lands spanning 54 years of recovery. Meanwhile, by synthesizing prior studies of microbial phylogeny in community assembly, we proposed two conceptual models to better explain our results. At early successional stages, the significantly increasing phylogenetic clustering of bacterial communities with soil age was co-determined by the environmental selection from soil vegetation cover and by bacterial heterogeneous responses that less phylogenetically similar bacteria differently expanded their population in response to the increasing resource availability in soil along succession. At later successional stages, bacterial community phylogenetic structures displayed progressively lower variability. The fungal community phylogenetic structures varied relatively less and were independent of soil age, soil properties and vegetation cover, which was attributed to the dominance of stochastic processes in community structure turnover along succession. Network analysis revealed a decrease in bacterial co-occurrence complexity along succession, which aligned with a decrease in average pairwise phylogenetic distances between co-occurring bacteria. These patterns together implied a decrease in potential bacterial cooperation that was probably mediated by increasing resource availability along succession. The increased complexity of fungal co-occurrence along succession was independent of the phylogeny between co-occurring fungi. This study provides new sights into ecological processes and mechanisms underlying bacterial and fungal community dynamics along ecological succession, thereby boosting our understanding of the interactions between microbial community assembly and soil environment gradients.