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，但原位追踪地下植食性动物的食物选择极具挑战。本研究开发了一套优化的聚合酶链式反应（PCR，Polymerase Chain Reaction）检测方法，利用靶向叶绿体trnT-F基因区间的通用植物引物，可从无脊椎动物肠道中检出植物脱氧核糖核酸（DNA）。基于该检测体系，我们评估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种植物饲喂幼虫，涵盖1种禾本科植物、1种豆科植物以及4种非豆科阔叶草本植物。此外，我们还探究了两个科学问题：一是能否扩增腐解植物的DNA，二是幼虫肠道内能否检出腐解植物食物的DNA。 在本次实验测试的最长消化时长72小时内，均可从幼虫肠道中检出摄入的植物根系DNA。当饲喂活体植物时，不同植物种类的DNA检出率存在显著差异，这可能与植物组织取食量、根系适口性、根系形态以及植物次生代谢产物的差异相关。 上述结果表明，植物种类会影响饲喂后植物DNA的检出成功率，在基于分子手段解析植物取食率时需将该因素纳入考量。 只要能从土壤中获取腐解植物组织，即可成功扩增其DNA；本检测体系也可验证幼虫对腐解植物组织的取食行为，但相较于腐解植物材料，幼虫似乎更偏好新鲜根系。