Dendritic stream networks are an intriguing subject for exploring the spatial and temporal variability of the rare and common bacterial biosphere, yet very few such studies have been conducted. We sampled riverine bacterioplankton at 13 sites in a subarctic riverine network across 3 years, with five sampling times each year. Ordinations showed a consistent pattern of downstream shift for both rare and abundant subcommunities. We also detected a temporal signal, with seasonal community shifts reflecting changes in water temperature and groundwater contribution, and an inter‐annual pattern where the year 2018 differed from other years. Phylogenetic turnover of the rare subcommunity indicated homogeneous selection, whereas the abundant subcommunity was mainly stochastically structured. Transiently rare taxa were the dominant type of rarity with the highest proportion at the headwater regions. The bacterioplankton community was characterized by a small group of core taxa that occurred at most sites with little temporal variation, a very large number of permanently or transiently rare taxa, and taxa shifting through time between the rare and abundant biosphere. While this basic structure could have been detected with less extensive temporal replication, a comprehensive understanding of the rare biosphere in riverine bacterioplankton can only be achieved via inter‐annual, spatially replicated sampling that covers the whole stream network.

中文翻译：

---

亚北极河流网络中的细菌稀有性：生物多样性模式、组装机制和稀有类型

树突流网络是探索稀有和常见细菌生物圈的空间和时间变异性的一个有趣的课题，但此类研究很少进行。我们在 3 年内对亚北极河流网络的 13 个地点的河流浮游细菌进行了采样，每年采样 5 次。对于稀有和丰富的亚群落来说，排序显示出一致的下游转移模式。我们还检测到一个时间信号，季节性群落变化反映了水温和地下水贡献的变化，以及 2018 年与其他年份不同的年际模式。稀有亚群的系统发育周转表明同质选择，而丰富的亚群主要是随机结构的。暂时稀有类群是稀有的主要类型，在源头地区比例最高。浮游细菌群落的特点是在大多数地点出现一小群核心类群，时间变化很小，有大量永久或短暂的稀有类群，以及随时间在稀有生物圈和丰富生物圈之间变化的类群。虽然这种基本结构可以通过不太广泛的时间复制来检测到，但对河流浮游细菌稀有生物圈的全面了解只能通过覆盖整个河流网络的年度间、空间复制采样来实现。