Spider webs as a source of environmental DNApodoktorski raziskovalni projekt
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 well-known shortcomings, e.g. labor intensiveness, rare taxonomic expertise, problematic diagnosis, invasive sampling, etc. Consequently, traditional approaches are often inadequate and cannot provide effort needed for environmental monitoring related to modern challenges, such as the rapid decline of biodiversity, climate change, and invasive species.
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. Several tissues from live or dead organisms represent potential sources of eDNA, e.g. urine, feces, integument, and extracellular DNA. Environmental DNA is present in all media, e.g. soil, sediment, water and permafrost, and depending on the medium, the preservation of eDNA varies from a few weeks to hundreds of thousands of years. Also, eDNA can be amplified either using specific primers within a single-species approach, or using generic primers in a multiple-species approach (i.e. DNA metabarcoding). Accordingly, eDNA is increasingly used to address fundamental questions in basic and applied research fields, such as ecology, molecular biology, nature conservation, and paleontology. In this context, I here propose to investigate the potential use of spider webs as a source of eDNA.
Spiders are enormously diverse and abundant, are dominant predators of arthropods, their webs are highly diverse in architecture, size and microhabitat, and they target a wide range of prey. In two recent studies, spider webs have been found to contain traces of spider and prey DNA. In this context, genetic material obtained from spider webs might represent a novel, non-invasive tool for identification of organisms, but remains almost unstudied. Because spider webs are abundant and can be easily collected, traces of eDNA on webs potentially represent an alternative to more traditional sampling methods. Furthermore, web eDNA may provide a new method of studying the interactions between spiders and their prey. Applied more broadly, eDNA from spider webs might provide a unique opportunity to address a variety of questions related to the study of arthropod communities in general, without the need to actually collect them. In addition to containing animal eDNA, spider webs might also contain other genetic material. For example, spider webs are known to passively collect pollen and fungal spores.
When using eDNA for inferences of the proximity of organisms relative to the traces of their DNA, it is crucial to also consider the spatial and temporal scales of eDNA. In this context, spider webs potentially represent a novel and powerful source of eDNA: they accumulate DNA from the air column, an underexplored eDNA source, and compared to sediment or water likely contain more detailed spatial and temporal information about the accumulated genetic material. In the proposed project, I aim to test whether different web types are suitable for obtaining eDNA, how DNA degrading factors, specifically UV light, heat and humidity affect eDNA detection success, and investigate whether specific web types are better at accumulating eDNA of specific organism groups, i.e. arthropods, fungi and plants. I expect the proposed research to provide the first platform for future research of web derived eDNA, with numerous potential uses, from fields like biodiversity monitoring, animal diet assessment, invasive species, climate change, to studies of arthropod, plant, and fungal communities, as well as testing web eDNA in a metabarcoding context.