It's raining species: Rainwash eDNA metabarcoding as a minimally invasive method to assess tree canopy invertebrate diversity

Abstract

Forest canopies are highly diverse ecosystems, but despite several decades of intense research, there remain substantial gaps in our knowledge of their biodiversity and ecological interactions. One fundamental challenge in canopy research is the limited accessibility of the ecosystem. Consequently, previous studies have relied on the ap-

Non-destructive collection and metabarcoding of arthropod environmental DNA remained on a terrestrial plant

“…In this study, we successfully detected eDNA of 42 additional species of which taxonomy was assigned at least to the genus level in overall 37 samples in addition to seven target species (Table S3 ) from two plant species only without harvesting any plant tissues. One study collecting rainfall under the canopies of four tree species with two replications for each species detected eDNA of 50 invertebrate species 19 . Another study collecting 56 individual flowers from seven plant species detected eDNA of 135 arthropod species in 67 families 16 .…”

“…In addition to that, periodic survey using our method by rainfall is difficult at a region of low precipitation and during low precipitation periods. However, plant flow collection method using the rainfall would make a great contribution to the study of arthropods associated with tall trees, to which it is difficult to spray water to a whole plant body artificially, as Macher et al 19 demonstrated. In areas such as tropical rainforests, where rain falls regularly and tall trees are dense, using rainfall would be recommended for our method.…”

“…eDNA metabarcoding has also been applied in terrestrial ecosystems to detect mammals living in forest ecosystems 14 , pollinators 15 , 16 , and local arthropod diversity 17 , 18 . However, eDNA metabarcoding has been rarely applied to organisms associated with terrestrial plants except for various pollinator species from flowers 16 and invertebrates from tree canopies 19 because methods to collect eDNA remaining on plant surfaces are still developing best practice advises. In several cases, the eDNA of herbivores remaining on plants has been successfully extracted using destructive methods 20 – 23 .…”

“…In order to disseminate this technique to detect pest insect attacks and apply it to large-scale biodistribution surveys (e.g., with citizen participants), we primarily aimed to evaluate a method of collecting eDNA using tap water, which is more convenient to use than distilled water in Japan. In addition, we investigated the effectiveness of collecting eDNA using rainfall, which has been suggested as a promising alternative in fields 19 as it can eliminate the need for manual water addition during the collection process. However, it should be noted that our study was not intended to identify the optimal water type for eDNA collection, as our sample size was small and the sequence size was unevenly distributed among the three water types (tap water, distilled water, and rainfall).…”

Plant‐derived environmental DNA complements diversity estimates from traditional arthropod monitoring methods but outperforms them detecting plant–arthropod interactions

“…eDNA is typically recovered from plant surfaces by washing it off with water and filtering the wash‐off (Allen et al., 2022; Macher et al., 2023; Valentin et al., 2020). However, washes are probably limited to taxa from the surface of the plant.…”