Towards working protocols for the use of eDNA from spider webs

The application of biological data to relevant societal problems is largely limited to correct specimen identification. Traditional species monitoring and specimen identification relies on morphological and behavioral character identification, but these methods have several wellknown shortcomings. For example, the vast majority of biodiversity is scientifically undescribed, some higher taxa are not monophyletic, and traditional, phenotypic data sources insufficiently diagnose species and higher taxa. Consequently, traditional approaches are often inadequate in performing efficient and standardized biodiversity surveys. For example, many species can only be identified in certain life stages and their identification is highly dependent on taxonomic expertise, which is often lacking or in decline. Additionally, traditional sampling techniques are sometimes invasive, especially in invertebrates and aquatic ecosystems. The traditional taxonomic process is mostly manual and time-consuming, and thus cannot provide the effort needed for environmental monitoring related to modern challenges, such as the rapid decline of biodiversity, climate change, and invasive species. The severe limitations to traditional methods urgently call for alternative approaches.

Novel molecular approaches such as sampling of environmental DNA (eDNA), i.e. obtaining genetic material directly from environmental samples in the absence of biological source material, can potentially overcome many limitations of traditional biodiversity monitoring. Environmental DNA can be obtained and amplified either using specific primers within a single-species approach, or using generic primers in a multiple-species approach, referred to as DNA metabarcoding (massive DNA sequencing in order to simultaneously identify multiple taxa). Accordingly, eDNA is increasingly used to address fundamental questions in basic and applied research fields, such as ecology, molecular biology, nature conservation, and paleontology. New approaches in both sampling of diverse environments and organisms, as well as bioinformatical data manipulation will likely lead to new valuable methodological insights. Our preliminary results from an ongoing pilot project (see below) show that spider webs are a good source of eDNA from diverse organisms, thus providing a new powerful tool, with a variety of potential applications. In this context, we here propose to develop working protocols for the use of eDNA from spider webs in three diverse and important research fields: classical biodiversity monitoring, monitoring of airborne microbiota, and detection of agricultural pests and invasive species.

We will address these fields in three work packages (WP). The goal of WP1 is to develop protocols for the use of eDNA from spider webs to complement classical sampling of spiders as the producers of these webs, bees of the superfamily Apoidea as potential spider prey and the most important pollinators, and vascular plants as organisms not in direct contact with webs. The goal of WP2 is to conduct pilot investigations into the utility of eDNA from spider webs as a complementary sampling tool of airborne microbiota. The goal of WP3 is to work towards developing protocols for the use of eDNA from spider webs in monitoring of fungal agricultural pests, and invasive plant and animal species. We will check whether spider webs in nature permit us to trace fungal agricultural pests known to occur in Slovenia, as well as detect some that are yet undocumented. Furthermore, we will develope protocols for using eDNA from spider webs to monitor representatives of the numerous invasive plants in the region, as well as Aedes mosquitos as a representative group of invasive animals.