Seasonal Trade-Offs Between Sedimentary Bacterial Generalists and Specialists Sustain Community Stability in Rivers

Deciphering the intrinsic coexistence mechanisms of generalists and specialists is crucial for maintaining biodiversity. However, how these taxa seasonally turn over to sustain the stability of bacterial communities remains poorly understood in river sediments. Here, we employed 16S rRNA gene amplicon sequencing and statistical analyses to investigate the diversity, assembly processes, and ecological state conversion of bacterial generalists and specialists in river ecosystems. Our results revealed that generalists exhibited significantly higher phylogenetic species variability (p < 0.001), whereas specialists demonstrated a stronger phylogenetic signal in ecological preferences (p < 0.05). Specialists were mainly shaped by stochastic processes (wet season: 91%; dry season: 86%), while the impact of stochasticity on generalists was distinct across different seasons (wet season: 65%; dry season: 35%). Co-occurrence network analysis revealed that generalists played a more important role than specialists in maintaining the stability of bacterial communities, with generalist communities (robustness: 0.46; vulnerability: 0.0059) themselves exhibiting higher stability than specialist communities (robustness: 0.34; vulnerability: 0.13). Nevertheless, ecological state conversion from specialists to generalists (conversion rate: 43.01) ensured the maintenance of stable biodiversity. Collectively, these findings underscore the importance of dynamic trade-offs between generalists and specialists in sustaining the stability of bacterial communities in river ecosystems.