Environmental DNA metabarcoding of cow dung reveals taxonomic and functional diversity of invertebrate assemblages

Insects and other terrestrial invertebrates are declining in species richness and abundance. This includes the invertebrates associated with herbivore dung, which have been negatively affected by grazing abandonment and the progressive loss of large herbivores since the Late Pleistocene. Importantly, traditional monitoring of these invertebrates is time-consuming and requires considerable taxonomic expertise, which is becoming increasingly scarce. In this study, we investigated the potential of environmental DNA (eDNA) metabarcoding of cow dung samples for biomonitoring of dung-associated invertebrates. From eight cow pats we recovered eDNA from 12 orders, 29 families, and at least 54 species of invertebrates (mostly insects), representing several functional groups. Furthermore, species compositions differed between the three sampled habitats of dry grassland, meadow, and forest. These differences were in accordance with the species’ ecology; for instance, several species known to be associated with humid conditions or lower temperatures were found only in the forest habitat. We discuss potential caveats of the method, as well as directions for future study and perspectives for implementation in research and monitoring.

昆虫及其他陆生无脊椎动物的物种丰富度与种群丰度正持续下滑。这其中亦包含与草食动物粪便相关的无脊椎动物类群；自更新世晚期以来，这类类群便因放牧活动弃置以及大型草食动物种群的逐步消亡而遭受负面影响。值得关注的是，针对这类无脊椎动物的传统监测工作耗时冗长，且亟需深厚的分类学专业知识，而此类专业人才正日益稀缺。本研究针对牛粪样本开展环境DNA（eDNA）元条形码（metabarcoding）检测，探究其在粪便相关无脊椎动物生物监测中的应用潜力。本次研究从8份牛粪样本中成功检出12个目、29个科的无脊椎动物eDNA，涵盖至少54个物种（绝大多数为昆虫），涉及多个功能类群。此外，在所采样的干旱草原、草甸与森林三种生境中，物种组成存在显著差异。这类差异与物种的生态习性高度契合：例如，若干已知偏好湿润环境或低温条件的物种，仅在森林生境中被检出。本研究同时讨论了该方法的潜在局限性，以及未来研究方向与在科研及监测工作中推广应用的前景。