Environmental quality affects the formation of generalist and specialist taxa in microbial communities

Microorganisms play a central role in global biogeochemical cycles, and generalists and specialists differ significantly in environmental adaptability, ecological functions, and community stability. However, current studies on generalists and specialists have mainly focused on habitat type or resource availability, while how habitat quality affects their geographic distribution and succession processes remains unclear. This study investigates how habitat quality influences the geographical distribution and community assembly of generalists and specialists. Using the Remote Sensing Ecological Index (RSEI), we assessed soil ecological quality in the Tarim River Basin and categorized the habitats into low-quality (extreme poor), moderate-quality (moderate poor), and high-quality (relatively good) zones. We analyzed the geographical patterns of generalists/specialists and their community assembly processes as habitat quality declined. Results indicated significant differences in microbial community composition (β-diversity, Bray-Curtis distance) between generalist and specialist groups across habitats. As RSEI decreased, the relative abundance of specialist microorganisms increased, while generalist microorganisms decreased. Microbial community assembly was shaped by both stochastic and deterministic processes, with stochastic processes accounting for >75%. Deterministic processes have a greater impact on specialists than generalists. This study provides insights into how environmental changes affect microbial ecosystems and their dynamics.