Microbial generalists and specialists in permafrost demonstrate disparate responses to extreme environments

Permafrost ecosystems, defined by their perpetually frozen substrates, harbor distinctive microbial assemblages that play critical roles in biogeochemical cycles. A thorough characterization of these microbial communities is essential for forecasting how permafrost environments will respond to ongoing climate perturbations. This study first systematically examines the ecological differentiation between microbial generalists and specialists along a ∼1000 km permafrost transect on the Tibetan Plateau, utilizing 16S rRNA gene sequencing analysis. Our results demonstrate significant spatial partitioning, with specialists displaying distinct layer-specific ASVs, while generalists maintained consistent distributions across layers. Notably, we identified critical mean annual temperature thresholds that trigger abrupt taxonomic shifts, including increased Subgroup_7 (Acidobacteriota) abundance (>-3.8 °C) and decreased Pseudarthrobacter (<-1.1 °C). Strikingly, generalist assemblages correlated strongly with soil clay content and primary productivity, whereas specialist communities exhibited greater dependence on nutrient availability. Specialists formed densely interconnected communities demonstrating maximal stability in surface layers (SUR), contrasting with the simpler, sparser networks of generalists that stabilized the subsurface layers (SUB). Stochastic processes were predominant for both groups, but deterministic selection played a stronger role in the specialist assembly. Remarkably, although both groups enhanced primary production, they operated through opposing mechanisms: generalists showed positive associations with key soil properties, whereas specialists exhibited negative associations. These findings elucidate the complementary functional roles of microbial generalists and specialists in maintaining the resilience of permafrost ecosystems under changing climatic conditions.