Although sedimentary ancient DNA (sedaDNA) has been increasingly used to study paleoecological dynamics (Schulte et al., 2020), the approach has rarely been compared with the traditional method of pollen analysis for investigating past changes in the vegetation composition and diversity of Arctic treeline areas. Here, we provide a history of latitudinal floristic composition and species diversity based on a comparison of sedaDNA and pollen data archived in three Siberian lake sediment cores spanning the mid-Holocene to the present (7.6–0 cal ka BP), from northern typical tundra to southern open larch forest in the Omoloy region. Our results show that the sedaDNA approach identifies more plant taxa found in the local vegetation communities, while the corresponding pollen analysis mainly captures the regional vegetation development and has its limitations for plant diversity reconstruction. Measures of alpha diversity were calculated based on sedaDNA data recovered from along a tundra to forest tundra to open larch forest gradient. Across all sites, sedaDNA archives provide a complementary record of the vegetation transition within each lake’s catchment, tracking a distinct latitudinal vegetation type range from larch tree/alder shrub (open larch forest site) to dwarf shrub-steppe (forest tundra) to wet sedge tundra (typical tundra site). By contrast, the pollen data reveal an open landscape, which cannot distinguish the temporal changes in compositional vegetation for the open larch forest site and forest-tundra site. Increasing Larix pollen percentages were recorded in the forest-tundra site in the last millenium although no Larix DNA was detected, suggesting that the sedaDNA approach performs better for tracking the local establishment of Larix. Highest species richness and diversity are found in the mid-Holocene (before 4.4 ka) at the typical tundra site with a diverse range of vegetational habitats, while lowest species richness is recorded for the forest tundra where dwarf-willow habitats dominated the lake’s catchment. During the late Holocene, strong declines in species richness and diversity are found at the typical tundra site with the vegetation changing to relatively simple communities. Nevertheless, plant species richness is mostly higher than at the forest-tundra site, which shows a slightly decreasing trend. Plant species richness at the open larch forest site fluctuates through time and is higher than the other sites since around 2.5 ka. Taken together, there is no evidence to suggest that the latitudinal gradients in species diversity changes are present at a millennial scale. Additionally, a weak correlation between the principal component analysis (PCA) site scores of sedaDNA and species richness suggests that climate may not be a direct driver of species turnover within a lake’s catchment. Our data suggest that sedaDNA and pollen have different but complementary abilities for reconstructing past vegetation and species diversity along a latitude.

中文翻译：

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从花粉和沉积古DNA看东北西伯利亚林线区的全新世植被和植物多样性变化

尽管沉积古 DNA (sedaDNA) 已越来越多地用于研究古生态动力学 (Schulte et al., 2020)，但该方法很少与传统的花粉分析方法进行比较，以研究过去北极林线植被组成和多样性的变化领域。在这里，我们提供了纬度植物区系组成和物种多样性的历史，该数据基于从北部典型苔原跨越中全新世到现在（7.6-0 cal ka BP）的三个西伯利亚湖泊沉积物核心中存档的 sedaDNA 和花粉数据的比较到奥莫洛伊地区南部开阔的落叶松林。我们的结果表明 sedaDNA 方法识别了在当地植被群落中发现的更多植物分类群，而相应的花粉分析主要捕捉区域植被发育情况，对植物多样性重建有其局限性。根据从苔原到森林苔原到开放落叶松林梯度恢复的 sedaDNA 数据计算 alpha 多样性的度量。在所有地点，sedaDNA 档案提供了每个湖泊流域内植被过渡的补充记录，跟踪从落叶松/桤木灌木（开放落叶松林地）到矮灌木草原（森林苔原）到湿莎草的不同纬度植被类型范围苔原（典型的苔原遗址）。相比之下，花粉数据揭示了一个开放的景观，无法区分开放落叶松林和森林苔原的植被组成的时间变化。尽管没有检测到落叶松 DNA，但在过去的千年里，森林苔原遗址记录了落叶松花粉百分比的增加，这表明 sedaDNA 方法在跟踪落叶松的本地建立方面表现更好。全新世中期（4.4 ka 之前）的物种丰富度和多样性最高，位于典型的苔原遗址，植被栖息地范围广泛，而森林苔原的物种丰富度最低，其中矮柳栖息地占湖泊集水区的主导地位。在全新世晚期，典型苔原遗址的物种丰富度和多样性急剧下降，植被向相对简单的群落转变。尽管如此，植物物种丰富度大多高于森林-苔原地，呈现出略有下降的趋势。开放落叶松林站点的植物物种丰富度随时间波动，自 2.5 ka 左右开始高于其他站点。总之，没有证据表明物种多样性变化的纬度梯度存在于千年尺度。此外，sedaDNA 的主成分分析 (PCA) 站点分数与物种丰富度之间的弱相关性表明，气候可能不是湖泊流域内物种更新的直接驱动因素。我们的数据表明，sedaDNA 和花粉具有不同但互补的能力，可以沿纬度重建过去的植被和物种多样性。没有证据表明物种多样性变化的纬度梯度存在于千年尺度。此外，sedaDNA 的主成分分析 (PCA) 站点分数与物种丰富度之间的弱相关性表明，气候可能不是湖泊流域内物种更新的直接驱动因素。我们的数据表明，sedaDNA 和花粉具有不同但互补的能力，可以沿纬度重建过去的植被和物种多样性。没有证据表明物种多样性变化的纬度梯度存在于千年尺度。此外，sedaDNA 的主成分分析 (PCA) 站点分数与物种丰富度之间的弱相关性表明，气候可能不是湖泊流域内物种更新的直接驱动因素。我们的数据表明，sedaDNA 和花粉具有不同但互补的能力，可以沿纬度重建过去的植被和物种多样性。