Trophic and Non-Trophic Interactions in a Biodiversity Experiment Assessed by Next-Generation Sequencing

Plant diversity affects species richness and abundance of taxa at higher trophic levels. However, plant diversity effects on omnivores (feeding on multiple trophic levels) and their trophic and non-trophic interactions are not yet studied because appropriate methods were lacking. A promising approach is the DNA-based analysis of gut contents using next generation sequencing (NGS) technologies. Here, we integrate NGS-based analysis into the framework of a biodiversity experiment where plant taxonomic and functional diversity were manipulated to directly assess environmental interactions involving the omnivorous ground beetle Pterostichus melanarius. Beetle regurgitates were used for NGS-based analysis with universal 18S rDNA primers for eukaryotes. We detected a wide range of taxa with the NGS approach in regurgitates, including organisms representing trophic, phoretic, parasitic, and neutral interactions with P. melanarius. Our findings suggest that the frequency of (i) trophic interactions increased with plant diversity and vegetation cover; (ii) intraguild predation increased with vegetation cover, and (iii) neutral interactions with organisms such as fungi and protists increased with vegetation cover. Experimentally manipulated plant diversity likely affects multitrophic interactions involving omnivorous consumers. Our study therefore shows that trophic and non-trophic interactions can be assessed via NGS to address fundamental questions in biodiversity research.植物多样性会影响更高营养级类群的物种丰富度与种群丰度。然而，由于缺乏合适的研究方法，植物多样性对杂食动物（取食多个营养级的生物）及其营养与非营养互作的影响尚未得到探索。采用下一代测序（Next Generation Sequencing, NGS）技术开展肠道内容物DNA分析，是一种颇具潜力的研究手段。本研究将基于NGS的分析方法整合至一项生物多样性实验框架内：该实验通过人为操控植物的分类多样性与功能多样性，以直接评估涉及杂食性步甲*Pterostichus melanarius*的各类环境互作。研究以步甲的反刍液为材料，使用针对真核生物的通用18S核糖体DNA（18S rDNA）引物开展基于NGS的分析。通过NGS方法，我们在反刍液中检测到了多样的类群，其中包含与*Pterostichus melanarius*存在营养互作、携播互作、寄生互作以及中性互作的生物类群。研究结果显示：（1）营养互作的发生频率随植物多样性与植被盖度的提升而升高；（2）集团内捕食的发生频率随植被盖度的增加而上升；（3）与真菌、原生生物等类群的中性互作频率同样随植被盖度提升而升高。经实验操控的植物多样性，大概率会影响涉及杂食性消费者的多营养级互作。因此，本研究证实，可通过NGS技术对营养与非营养互作进行评估，以解答生物多样性研究中的核心科学问题。