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, since 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 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.

分子生物技术的新近进展，使得我们得以解析未被充分研究的类群的食性。蜻蛉目（Odonates）是诸多昆虫类群潜在的重要下行调控因子。然而截至目前，学界对蜻蛉目昆虫捕食习性的认知，主要源自对其捕猎或取食行为的有限现场观测。本研究以芬兰西南部某样地的三种成虫蜻蛉目物种——狭翅丝蟌（Lestes sponsa）、蓝纹尾蟌（Enallagma cyathigerum）和赤褐蜻（Sympetrum danae）——为研究对象，探究宏条形码（metabarcoding）技术在解析其食性方面的应用潜力。为此，我们对比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。基于上述提取产物，我们对共计72头蜻蛉目个体的类群特异性线粒体标记基因（COI与16S rRNA）进行了扩增，并将扩增结果与全面的参考数据库进行比对。三种蜻蛉目昆虫的食性存在显著重叠，且不同体型、性别的个体间未呈现显著食性差异，这反映出成虫蜻蛉目昆虫的机会主义觅食策略。本次研究共检测到41种不同的猎物类群，其中取食频率最高的为双翅目（Diptera）物种，此外还记录到其他6个昆虫纲目的类群。基于本研究数据，传统盐析法为最优的DNA提取方案：其不仅能获取最多的猎物组分信息，同时也是最为经济的方法。据我们所知，本研究首次实现了蜻蛉目昆虫的物种级食性解析。在合理规避方法学局限性的前提下，我们后续可进一步探究蜻蛉目昆虫在陆地与水生食物网中的生态功能，以及其在两类生境间传递营养补给的作用。