Fake webs, real results: Artificial spiderwebs for eDNA collection

Abstract

Environmental DNA (eDNA)-based detection is a valuable biomonitoring tool that is well-developed for water, soil, and scat substrates. Emergent research is focusing on air as a new substrate, including opportunistically collected natural spiderwebs which may have negative impacts on local spider diversity. Here, we design novel artificial spiderwebs and compare their effectiveness with natural spiderwebs and aquatic eDNA approaches for biomonitoring of terrestrial taxa. A total of 33 eDNA samples (18 water, 6 natural spiderwebs, 9 artificial spiderwebs) were collected from a rural property in Palmerston North (Aotearoa New Zealand). Three amplicons (COI, 16S, and ITS) were sequenced for each sample to evaluate the performance of each collection method for detecting invertebrates, vertebrates, and plant/algal taxa. The 16S amplicon performed best in terms of sequencing output and consistency, as well as species accumulation curves, with the COI dataset performing worst for all eDNA collection methods. Alpha diversity varied by amplicon and collection method in both value and consistency among samples, with 16S and ITS retrieving higher diversity for water samples and both artificial and natural webs outperforming water in fungal COI diversity recovery. Ordination plots showed clear differences in sample similarity across biomes, with all three amplicons showing differentiation between water and either web type. However, specialist species were recovered by each of the two web types, with artificial webs consistently recovering more unique diversity than natural webs. Our results suggest that artificial spiderwebs could be a promising new method in the eDNA biomonitoring toolbox, providing biodiversity data that complements water-based collections and, depending on the research question, may serve as a sufficient proxy for natural spiderweb studies.