Metabarcoding has proven to be a powerful tool to assess ecological patterns and diversity from different habitats. Terrestrial invertebrate diversity is frequently based on bulk samples, which require comparatively high sampling efforts. With environmental DNA (eDNA) metabarcoding, field sampling effort can be reduced while increasing number of recovered organism groups. However, a proof of concept is missing for several invertebrate groups, hampering the development of best-practice advice for these groups. This study aims to provide recommendations on key aspects for the processing of soil samples, from sampling effort to choice of DNA extraction method and marker genes. This study uses eDNA metabarcoding as a tool for assessing invertebrate biodiversity in soil samples, specifically comparing two DNA extraction methods (with and without a lysis step) and two marker genes, 18S and COI. The results show that the choice of marker and DNA extraction method significantly affect species detection rates and concomitantly observed invertebrate community composition. Combining methods, by using larger amounts of starting material and including a lysis step resulted in an increase of invertebrate species numbers. Together, these methods improved the detection of species with known lower population densities and allowed the assessment of temporary mesofauna. Furthermore, the choice of marker significantly influenced the diversity levels found. The 18S marker allowed the detection of a higher number of annelid and nematode OTUs, while the COI marker was more suitable for detecting changes in arthropod community structure especially at the species level. This study makes significant advances to the field of invertebrate biodiversity assessment, particularly using metabarcoding tools by addressing several methodological considerations that are key for accurate ecological appraisals.

中文翻译：

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发掘土壤eDNA元条形码的潜力-寻求无脊椎动物生物多样性评估的最佳实践建议

事实证明，元条形码是评估不同生境的生态模式和多样性的有力工具。陆地无脊椎动物多样性通常基于大量样本，这需要相对较高的抽样工作。使用环境DNA（eDNA）元条形码，可以减少现场采样的工作，同时增加回收的生物体的数量。但是，一些无脊椎动物群体缺少概念证明，这妨碍了为这些群体提供最佳实践建议。这项研究旨在为土壤样品处理的关键方面提供建议，从采样工作到DNA提取方法和标记基因的选择。这项研究使用eDNA元条形码作为评估土壤样品中无脊椎动物生物多样性的工具，具体比较两种DNA提取方法（有和没有裂解步骤）和两个标记基因18S和COI。结果表明，标记物的选择和DNA提取方法显着影响物种检出率，并同时观察到无脊椎动物群落组成。通过使用大量的起始原料并包括裂解步骤的组合方法导致无脊椎动物种类数量的增加。总之，这些方法改善了已知种群密度较低的物种的检测，并允许评估临时中型动物。此外，标记的选择显着影响发现的多样性水平。18S标记可检测到更多的线虫和线虫OTU，而COI标记更适合检测节肢动物群落结构的变化，尤其是在物种水平上。这项研究在无脊椎动物生物多样性评估领域取得了重大进展，尤其是通过使用元条形码工具，解决了对准确生态评估至关重要的几种方法上的考虑。