Microbial co-occurrence patterns and community assembly in seamount sediment cores: disentangling the effects of assembly processes on β-diversity.

Seamounts are hotspots of seafloor biodiversity in the open sea, and microorganisms are the base of seamount food webs. However, the mechanism shaping the vertical distribution patterns of microbial community composition in seamount sediment cores remains elusive. Here, we analyzed the microbial communities in seven sediment cores collected from a seamount in the Western Philippine Ocean and its adjacent valley. We investigated the assembly of bacterial and archaeal communities in three sediment cores that contained complete profiles of microbial communities and deciphered how changes in community assembly processes altered β-diversity. In addition, we explored the microbial co-occurrence patterns in the three cores and their correlation with environmental variables. The results revealed that bacterial community assembly was dominated by drift, dispersal limitation, homogenizing dispersal, and homogeneous selection, whereas archaeal community assembly was dominated by drift. Besides, the variability of microbial co-occurrence patterns among the three sediment cores was driven mainly by trace elements. This study supported that dispersal limitation led to a higher β-diversity, whereas homogeneous selection, homogenizing dispersal, and drift resulted in a relatively lower β-diversity. Overall, this study offers key insights into the microbial occurrence patterns and community assembly in seamount sediment cores, and illustrates how different community assembly processes affect β-diversity.IMPORTANCEβ-Diversity (site-to-site variation in species composition) is important for understanding the mechanisms that generate and maintain biodiversity, but the origin of β-diversity is still largely unknown. Variations in β-diversity can be related to changes in assembly processes, but there is still a lack of a quantitative evaluation for the effects of different assembly processes on β-diversity. Here, we investigated the microbial community assembly in three sediment cores collected from a seamount in the Western Philippine Ocean and its adjacent valley. We compared the differences in β-diversity among bacterial communities that were driven by different assembly processes and found that β-diversity was enhanced by dispersal limitation but decreased by homogeneous selection, homogenizing dispersal, and drift. Our findings underscore the differential impacts of assembly processes on β-diversity, which advances the understanding of the origin of β-diversity.