Tao Li

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. IMPORTANCE: β-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.

Community composition is determined by four processes: drift, selection, dispersal, and speciation. The crucial issue in understanding community assembly is disentangling the relative importance of those processes. However, this issue has not been adequately addressed in benthic foraminiferal communities. A comprehensive study of benthic foraminiferal community composition, co‐occurrence network, and community assembly was conducted on the Xisha carbonate platform. The community composition was determined via the environmental DNA (eDNA) technique. Heavy metals (Co, Cr, Cu, Ni, Pb, V, and Zn), grain size, loss on ignition (LOI), organic carbon, and pH were chosen for environmental measurement. We evaluated the effects of environmental variables on the community composition and the co‐occurrence network, revealing that the former was affected only by organic carbon, whereas the latter was affected by both organic carbon and pH. Null and neutral models demonstrated that foraminiferal community assembly was driven by ecological drift instead of selection. The β‐NTI (a measure of the relative importance of deterministic and stochastic processes) had strong and positive correlations with community β‐diversity (compositional differences between pairs of communities) and network β‐diversity (structural differences between pairs of subnetworks). A conceptual model was offered to explain how heterogeneous selection and stochastic processes interact to affect the two β‐diversities. This study is the first to quantitatively assess the effects of variation in the relative importance of deterministic and stochastic processes on community β‐diversity and network β‐diversity in foraminifera; it provides new insight into the mechanisms underlying β diversity.

Community composition is determined largely by drift, selection, dispersal, and speciation. The crucial issue is disentangling the relative importance of different processes in community assembly. However, this issue has not been adequately discussed in benthic foraminiferal communities. Here, we studied the community composition, co-occurrence network, and community assembly of benthic foraminifera (protozoa) on the Xisha carbonate platform and their coupled relationships. The community composition was determined via the environmental DNA (eDNA) technique. Heavy metals, grain sizes, loss on ignition (LOI), organic carbon, and pH were measured for environmental assessment. The results showed that spatial variations in foraminiferal community composition were mainly controlled by organic carbon, whereas the effects of other variables were minimal. Similarly, spatial variations in the co-occurrence network were determined by organic carbon and pH. Despite the impacts of environmental variables on community composition, null and neutral models demonstrated that foraminiferal community assembly is driven by ecological drift instead of selection. This study is the first to couple community composition and co-occurrence networks with community assembly processes. A hypothesis was proposed that selection increases community heterogeneity and network heterogeneity, whereas stochastic processes eliminate such heterogeneities. This mechanism would bridge the gap between processes and community patterns. A comparison with our previous study revealed that foraminiferal community assembly may depend on specific systems (habitats). This insight could inform new strategies for the conservation of marine biodiversity.

Popular online publishers produce huge amount of news articles every day, so it is important to summarize the most up-to-the-minute information to help users quickly know the progresses of their interested news events. In this paper, we develop NewsCubeSum, a novel personalized news summarization system utilizing OLAP and supervised sentence selection techniques to generate brief summaries delivering news updates in multiple dimensions (such as time, entity, and topic). An illustrative case study and experimental results on summarization performance comparisons are provided to show the effectiveness of NewsCubeSum.