Distinct strategies of microeukaryotic generalists and specialists in Qinghai-Tibet plateau sediment driven by salinity.

Unraveling how microeukaryotic generalists and specialists assemble and coexist under environmental stress is central to our understanding of the mechanisms maintaining diversity. Here, we explored the biogeographical distributions of microeukaryotic generalists and specialists in lake surface sediments along a salinity gradient on the Qinghai-Tibet Plateau. We found that relative abundances of Chlorophyta (28.6 %) and Dinophyceae (9.5 %) were higher as habitat generalists than as specialists. Conversely, relative abundances of habitat specialists were higher in the Ciliophora (22.2 %) and Cercozoa (11.6 %) than those of generalists. Environmental adaptation analysis showed a broader niche threshold for generalists than for specialists, whereas a stronger phylogenetic signal for environmental factors was observed for specialists. Thus, increases in salinity had stronger effects on specialists than on generalists through environmental selection and diversification processes. However, null model analysis indicated stochastic processes were the primary drivers of both generalists and specialists. Network analysis revealed that with increasing salinity, specialists were more important than generalists in stabilizing networks. In addition, phylogenetic relatedness indicated that microeukaryotic generalists coexisted because of niche differences, whereas specialists coexisted because of average fitness similarity. Our study will help to predict microeukaryotic responses to environmental changes in aquatic ecosystems.