Rare biosphere represents the majority of Earth's biodiversity and performs vital ecological functions, yet little is known about its biogeographical patterns and community assembly processes in terrestrial ecosystems. Herein, we investigated the community composition and phylogeny of rare (relative abundance <0.1%) and abundant (>1%) bacteria in dryland grassland soils on the Tibetan Plateau. Results revealed similar biogeographical patterns of rare and abundant bacteria at both compositional and phylogenetic levels, but rare subcommunity was more heavily influenced by stochasticity (72%) than the abundant (57%). The compositional variation of rare bacteria was less explained by environmental factors (41%) than that of the abundant (80%), while the phylogeny of rare bacteria (36%) was more explained than that of the abundant (29%). The phylogeny of rare bacteria was equally explained by local factors (soil and vegetation) and geospatial distance (11.5% and 11.9% respectively), while that of the abundant was more explained by geospatial distance (22.1%) than local factors (11.3%). Furthermore, a substantially tighter connection between the community phylogeny and composition was observed in rare (R 2 = 0.65) than in abundant bacteria (R 2 = 0.08). Our study provides novel insights into the assembly processes and biographical patterns of rare and abundant bacteria in dryland soils.

Salinity is one of the most important environmental factors influencing bacterial plankton communities in lake waters, while its influence on bacterial interactions has been less explored. Here, we investigated the influence of salinity on the bacterial diversity, interactions and community structure in Tibetan Plateau lakes. Our results revealed that saline lakes (salinity between 0.5 and 50 g/L) harboured similar or even higher bacterial diversity compared with freshwater lakes (&lt; 0.5 g/L), while hyper-saline lakes (&gt; 50 g/L) exhibited the lowest diversity. Network analysis demonstrated that hyper-saline lakes exhibited the highest network complexity, with higher total correlation numbers (particularly the negative correlations), but lower network module numbers than freshwater and saline lakes. Furthermore, salinity dominantly explained the bacterial community structure variations in saline lakes, while those in freshwater and hyper-saline lakes were predominately explained by water temperature and geospatial distance, respectively. The core operational taxonomic units (OTUs), which were ubiquitously present in all lakes, were less sensitive to enhancing salinity than the indicative OTUs whose presence was dependent on lake type. Our findings offer a new understanding of how salinity influences bacterial community in plateau lakes.