Abstract Aim This study investigates taxonomic and phylogenetic diversity in diatom genera to evaluate assembly rules for eukaryotic microbes across the Siberian tree line. We first analysed how phylogenetic distance relates to taxonomic richness and turnover. Second, we used relatedness indices to evaluate if environmental filtering or competition influences the assemblies in space and through time. Third, we used distance-based ordination to test which environmental variables shape diatom turnover. Location Yakutia and Taymyria, Russia: we sampled 78 surface sediments and a sediment core, extending to 7,000Â years before present, to capture the forest-tundra transition in space and time respectively. Taxon Arctic freshwater diatoms. Methods We applied metabarcoding to retrieve diatom diversity from surface and core sedimentary DNA. The taxonomic assignment binned sequence types (lineages) into genera and created taxonomic (abundance of lineages within different genera) and phylogenetic datasets (phylogenetic distances of lineages within different genera). Results Contrary to our expectations, we find a unimodal relationship between phylogenetic distance and richness in diatom genera. We discern a positive relationship between phylogenetic distance and taxonomic turnover in spatially and temporally distributed diatom genera. Furthermore, we reveal positive relatedness indices in diatom genera across the spatial environmental gradient and predominantly in time slices at a single location, with very few exceptions assuming effects of competition. Distance-based ordination of taxonomic and phylogenetic turnover indicates that lake environment variables, like HCO3 and water depth, largely explain diatom turnover. Main conclusion Phylogenetic and abiotic assembly rules are important in understanding the regional assembly of diatom genera across lakes in the Siberian tree line ecotone. Using a space-time approach we are able to exclude the influence of geography and elucidate that lake environmental variables primarily shape the assemblies. We conclude that some diatom genera have greater capabilities to adapt to environmental changes, whereas others will be putatively replaced or lost due to the displacement of the Arctic tundra biome under recent global warming.

中文翻译：

---

北极硅藻属的系统发育多样性与环境形成组装规律——近古沉积DNA研究

摘要 目的本研究调查硅藻属的分类学和系统发育多样性，以评估西伯利亚树木线真核微生物的组装规则。我们首先分析了系统发育距离与分类丰富度和周转的关系。其次，我们使用相关性指数来评估环境过滤或竞争是否会在空间和时间上影响程序集。第三，我们使用基于距离的排序来测试哪些环境变量会影响硅藻周转。地点俄罗斯雅库特和泰米里亚：我们对 78 个表层沉积物和一个沉积物核心进行了采样，延伸至 7,000 年前，以分别捕捉森林-苔原在空间和时间上的转变。分类群北极淡水硅藻。方法我们应用元条形码从地表和核心沉积 DNA 中检索硅藻多样性。分类分配将序列类型（谱系）归入属并创建分类（不同属内谱系的丰富性）和系统发育数据集（不同属内谱系的系统发育距离）。结果与我们的预期相反，我们发现系统发育距离和硅藻属丰富度之间存在单峰关系。我们发现在空间和时间上分布的硅藻属中，系统发育距离和分类学更新之间存在正相关关系。此外，我们揭示了跨空间环境梯度的硅藻属的正相关性指数，主要是在单个位置的时间片中，假设竞争影响的情况很少。基于距离的分类学和系统发育周转排序表明湖泊环境变量，像 HCO3 和水深，很大程度上解释了硅藻的周转。主要结论 系统发育和非生物组装规则对于理解西伯利亚林线交错带中跨湖泊硅藻属的区域组装非常重要。使用时空方法，我们能够排除地理的影响并阐明湖泊环境变量主要塑造组件。我们得出的结论是，一些硅藻属具有更强的适应环境变化的能力，而其他硅藻属可能会因近期全球变暖导致北极苔原生物群落的位移而被取代或消失。使用时空方法，我们能够排除地理的影响并阐明湖泊环境变量主要塑造组件。我们得出的结论是，一些硅藻属具有更强的适应环境变化的能力，而其他硅藻属可能会因近期全球变暖导致北极苔原生物群落的位移而被取代或消失。使用时空方法，我们能够排除地理的影响并阐明湖泊环境变量主要塑造组件。我们得出的结论是，一些硅藻属具有更强的适应环境变化的能力，而其他硅藻属可能会因近期全球变暖导致北极苔原生物群落的位移而被取代或消失。