Detecting flying insects using car nets and DNA metabarcoding

Abstract

Monitoring insects across space and time is challenging, due to their vast taxonomic and functional diversity. This study demonstrates how nets mounted on rooftops of cars (car nets) and DNA metabarcoding can be applied to sample flying insect richness and diversity across large spatial scales within a limited time period. During June 2018, 365 car net samples were collected by 151 volunteers during two daily time intervals on 218 routes in Denmark. Insect bulk samples were processed with a DNA metabarcoding protocol to estimate taxonomic composition, and the results were compared to known flying insect richness and occurrence data. Insect and hoverfly richness and diversity were assessed across biogeographic regions and dominant land cover types. We detected 15 out of 19 flying insect orders present in Denmark, with high proportions of especially Diptera compared to Danish estimates, and lower insect richness and diversity in urbanized areas. We detected 319 species not known for Denmark and 174 species assessed in the Danish Red List. Our results indicate that the methodology can assess the flying insect fauna at large spatial scales to a wide extent, but may be, like other methods, biased towards certain insect orders.

Flying insect biomass is negatively associated with urban cover in surrounding landscapes

“…The measurements of the net were as follows: front height: 75 cm; front width: 100 cm; length: 140 cm; width of sampling bag: 29 cm; mesh size at the bottom (grey fabric): 2 × 1 mm; and mesh size for the rest of the net (white fabric): ~0.3 mm. Custom tent poles (L: 209 cm, D: 8 mm) supported the opening of the net (see also Supplementary Information in Svenningsen et al (2021)).…”

Emerging technologies revolutionise insect ecology and monitoring

“…Citizens have also helped to compile the training data needed for machine learning, for example, in the PollinatorWatch project (https:// www.zooniverse.org/projects/tokehoye/pollinatorwatch). In projects using DNA technology, some rely on citizen scientists for the collection of the insect samples [105], which are subsequently processed by scientists. A few citizen science projects are starting to include citizens in the analysis steps (e.g., the DNA&life project in Denmark) [106].…”

Current State of DNA Barcoding of Sciaroidea (Diptera)—Highlighting the Need to Build the Reference Library

“…Imbedded in the original development of DNA barcoding was, however, an essential subgoal to build a reference library where quality-checked, named specimens identified by means of classical morphological methods and deposited in voucher collections are linked to their barcodes and so-called barcode index numbers (BINs) [18]. So far, rather modest funding and efforts have been allocated to this endeavor while more and more studies uncritically use BINs to represent proxies for species [19] or uncritically extract names from the Barcode of Life online database BoldSystems (BOLD) and GenBank without validating their sources and quality [20,21]. For instance, Svenningsen et al [20], in a study detecting flying insects using car nets and DNA metabarcoding, claimed they documented 319 species not previously known from Denmark.…”

“…So far, rather modest funding and efforts have been allocated to this endeavor while more and more studies uncritically use BINs to represent proxies for species [19] or uncritically extract names from the Barcode of Life online database BoldSystems (BOLD) and GenBank without validating their sources and quality [20,21]. For instance, Svenningsen et al [20], in a study detecting flying insects using car nets and DNA metabarcoding, claimed they documented 319 species not previously known from Denmark. When checking the species of Mycetophilidae on their list, it was found that all five species claimed new to Denmark were not new but appeared new due to misspellings, synonyms, and different genus combinations.…”