Data from: Pellets of proof: first glimpse of the dietary composition of adult odonates as revealed by metabarcoding of feces

Recent advances in molecular techniques allow us to resolve the diet of unstudied taxa. Odonates are potentially important top-down regulators of many insects. Yet, to date, our knowledge of odonate prey use is based mainly on limited observations of odonates catching or eating their prey. In this study, we examine the potential use of metabarcoding in establishing the diet of three adult odonate species (Lestes sponsa, Enallagma cyathigerum, and Sympetrum danae) at a site in southwestern Finland. To this purpose, we compared three different methods for extracting DNA from fecal samples: the Macherey-Nagel Nucleospin XS kit, a traditional salt extraction, and the Zymo Research Fecal Microprep kit. From these extracts, we amplified group-specific mitochondrial markers (COI and 16S rRNA) from altogether 72 odonate individuals, and compared them to comprehensive reference libraries. The three odonate species show major overlap in diet, with no significant differences between individuals of different size and/or gender, reflecting opportunistic foraging of adult odonates. Of a total of 41 different prey species detected, the most frequently consumed ones were Diptera, with additional records of six other orders. Based on our data, the best DNA extraction method is the traditional salt extraction, as it provides the most information on prey content while also being the most economical. To our knowledge, this is the first study to resolve the species-level diet of adult odonates. Armed with the appropriate methodological caveats, we are ready to examine the ecological role of odonates in both terrestrial and aquatic food webs, and in transferring subsidies between these two realms.近年来分子技术的进步，使得我们能够解析尚未被研究类群的食性。蜻蛉目（Odonata）是诸多昆虫潜在的重要自上而下调控因子。然而迄今为止，我们对蜻蛉目昆虫猎物利用的认知，主要基于其捕获或取食猎物的有限观察记录。本研究旨在探究宏条形码（metabarcoding）技术在确定芬兰西南部某样地中三种成年蜻蛉目物种（Lestes sponsa、Enallagma cyathigerum及Sympetrum danae）食性方面的应用潜力。为此，我们比较了三种从粪便样本中提取DNA的方法：Macherey-Nagel Nucleospin XS试剂盒、传统盐析法以及Zymo Research Fecal Microprep试剂盒。我们从总计72只蜻蛉目个体的提取物中，扩增了类群特异性线粒体标记基因（细胞色素c氧化酶亚基I（COI）与16S核糖体RNA（16S rRNA）），并将扩增产物与全面的参考数据库进行比对。结果显示，这三种蜻蛉目物种的食性存在显著重叠，且不同体型、性别的个体之间并无显著差异，这反映了成年蜻蛉目昆虫的机会主义觅食策略。在总计检测到的41种不同猎物物种中，取食频率最高的为双翅目（Diptera），此外还记录到另外6个昆虫目类群。基于本研究数据，最优的DNA提取方法为传统盐析法，该方法不仅可获取最多的猎物组分信息，同时也是最为经济的方案。据我们所知，本研究首次解析了成年蜻蛉目昆虫的物种级食性。在合理规避方法学局限后，我们得以进一步探究蜻蛉目昆虫在陆地与水生食物网中的生态作用，以及其在这两类生境间的营养补贴转移。