Data from: The effect of plant identity and the level of plant decay on molecular gut content analysis in a herbivorous soil insect

Plant roots represent an important food source for soil-dwelling animals, but tracking herbivore food choices below-ground is difficult. Here, we present an optimized PCR assay for the detection of plant DNA in the guts of invertebrates, using general plant primers targeting the trnT-F chloroplast DNA region. Based on this assay, we assessed the influence of plant identity on the detectability of ingested plant DNA in Agriotes click beetle larvae. Six different plant species were fed to the insects, comprising a grass, a legume, and four non-legume forbs. Moreover, we examined whether it is possible to amplify DNA of decaying plants and if DNA of decayed plant food is detectable in the guts of the larvae. DNA of the ingested roots could be detected in the guts of the larvae for up to 72 h post-feeding, the maximum digestion time tested. When fed with living plants, DNA detection rates differed significantly between the plant species. This may be ascribed to differences in the amount of plant tissue consumed, root palatability, root morphology and/or secondary plant components. These findings indicate that plant identity can affect post-feeding DNA detection success, which needs to be considered for the interpretation of molecularly derived feeding rates on plants. Amplification of plant DNA from decaying plants was possible as long as any tissue could be retrieved from the soil. The consumption of decaying plant tissue could also be verified by our assay, but the insects seemed to prefer fresh roots over decaying plant material.植物根系是土壤栖息动物的重要食物来源，但在地下追踪植食动物的取食选择颇具难度。本研究采用靶向trnT-F叶绿体DNA区域的通用植物引物，建立了可检测无脊椎动物肠道内植物DNA的优化聚合酶链式反应（PCR）检测体系。基于该检测体系，我们探究了植物种类对叩甲属（Agriotes）幼虫肠道内摄入植物DNA检出率的影响。实验中共选取6种不同植物饲喂试虫，涵盖1种禾本科植物、1种豆科植物以及4种非豆科杂类草。此外，我们还验证了两个科学问题：一是能否扩增腐解植物的DNA，二是幼虫肠道内是否可检出腐解植物食物的DNA。在本次实验测试的最长消化时长（取食后72小时）内，均可在幼虫肠道中检测到摄入的植物根系DNA。当饲喂鲜活植物时，不同植物种类的DNA检出率存在显著差异，该差异可归因于取食植物组织量、根系适口性、根系形态以及/或植物次生代谢成分的差异。上述研究结果表明，植物种类会影响取食后DNA的检出成功率，在基于分子手段解析植物取食率时，需将这一因素纳入考量范畴。只要能从土壤中获取腐解植物组织，即可成功扩增得到其植物DNA。本检测体系同样可验证试虫对腐解植物组织的取食行为，但结果显示，试虫似乎更偏好取食鲜活根系而非腐解植物材料。