Data from: Molecular and pollen-based vegetation analysis in lake sediments from central Scandinavia

Plant and animal biodiversity can be studied by obtaining DNA directly from the environment. This new approach in combination with the use of generic barcoding primers (metabarcoding) has been suggested as complementary or alternative to traditional biodiversity monitoring in ancient soil sediments. However, the extent to which metabarcoding truly reflects plant composition remains unclear, as does its power to identify species with no pollen or macrofossil evidence. Here, we compared pollen-based and metabarcoding approaches to explore the Holocene plant composition around two lakes in central Scandinavia. At one site, we also compared barcoding results with those obtained in earlier studies with species-specific primers. The pollen analyses revealed a larger number of taxa (46), of which the majority (78%) was not identified by metabarcoding. The metabarcoding identified 14 taxa (MTUs), but allowed identification to a lower taxonomical level. The combined analyses identified 52 taxa. The barcoding primers may favour amplification of certain taxa, as they did not detect taxa previously identified with species-specific primers. Taphonomy and selectiveness of the primers are likely the major factors influencing these results. We conclude that metabarcoding from lake sediments provides a complementary, but not an alternative, tool to pollen analysis for investigating past flora. In the absence of other fossil evidence, metabarcoding gives a local and important signal from the vegetation, but the resulting assemblages show limited capacity to detect all taxa, regardless of their abundance around the lake. We suggest that metabarcoding is followed by pollen analysis and the use of species-specific primers to provide the most comprehensive signal from the environment.

通过直接从环境中获取DNA，可开展动植物生物多样性研究。这一结合通用条形码引物（generic barcoding primers）使用的元条形码（metabarcoding）技术，已被提议作为古老土壤沉积物中传统生物多样性监测的补充或替代方案。然而，元条形码技术能否真实反映植物群落组成，以及其能否识别出无花粉或大化石（macrofossil）证据的物种，目前仍不明确。本研究对比了基于花粉的分析方法与元条形码技术，以探究斯堪的纳维亚中部两处湖泊周边的全新世（Holocene）植物群落组成。在其中一个采样点，我们还将元条形码结果与此前利用物种特异性引物开展的研究结果进行了比对。花粉分析共检出46个类群，其中绝大多数（78%）未被元条形码技术识别。元条形码技术共检出14个分子分类单元（MTUs），但其鉴定的分类学层级更低。联合分析共检出52个类群。该通用条形码引物可能存在类群偏好性扩增，因为其未能检测到此前通过物种特异性引物识别出的类群。引物的埋藏学特性与扩增选择性，可能是影响上述结果的主要因素。我们得出结论：湖泊沉积物元条形码技术可作为花粉分析的补充工具，但无法替代后者，用于研究古植被。在缺乏其他化石证据的情况下，元条形码技术能够提供该湖泊周边植被的本地化重要信号，但其检出的类群组合无法覆盖所有类群，无论这些类群在湖区的丰度如何。我们建议，可将元条形码技术与花粉分析相结合，并辅以物种特异性引物的使用，以获取最全面的环境信号。