the study of bacteria elevational diversity pattern

The elevational diversity pattern and mechanisms underlying microbial community assembly along the elevational gradient is still understudied. Using a high-throughput sequencing technique, we collected 99 samples and examined the biodiversity patterns for soil bacterial communities along 1800-4100 m elevations on Gongga Mountain in China. Proteobacteria, Acidobacteria, Bacteroidetes, Chloroflexi and Planctomycetes predominated in the studied soils. The diversity (richness and Faith’s PD) decreased steeply as elevation increased from 2600-2800 m, thus an non-continuous decline in alpha diversity was observed. Though multiple factors showed relationships with bacterial alpha diversity, soil pH could be the best predictor. Bacterial communities differed significantly between lower (1800-2600 m) and higher (2800-4100 m) elevations of this study, and soil pH, temperature and precipitation could be the most three important factors shaping bacterial community structure. Null model analysis suggested that the deterministic environmental filtering played an overwhelming role in community assembly along the elevational gradient. Further variation partition analysis revealed that environmental variables explained a much larger fraction (14.79%) of the ß-diversity at lower elevations than by spatial variables (2.44%). However, spatial variables explained an increased proportion up to 13.87% of the ß-diversity at higher elevations, comparable to the 9.93% of environmental variables. The results suggested that dispersal limitation played an increased role at higher elevations. Our results highlighted the importance of soil pH, precipitation and temperature effect on bacterial community composition and structure, as well as an elevation-dependent role of dispersal limitation on soil bacterial community assembly along the elevational gradient of mountain ecosystem.