# A DNA Barcode Inventory of Austrian Dragonfly and Damselfly (Insecta: Odonata) Species

## TL;DR

This study creates a DNA barcode library for 78 Austrian dragonfly and damselfly species to support biodiversity monitoring and conservation efforts.

## Contribution

The study provides a comprehensive DNA barcode library for Austrian dragonflies and damselflies using COI and 16S markers.

## Key findings

- More than 90% of the DNA sequences for COI and 16S markers were successfully obtained and identified.
- Both COI and 16S markers proved effective for species identification in most odonate families.
- Challenges were observed in closely related genera with low genetic differences, but overall results were reliable.

## Abstract

Dragonflies and damselflies are good indicators of the health of rivers, ponds, and wetlands. In Austria, 78 species of these insects have been recorded. While we know a lot about where they live and how threatened they are, genetic data have been largely lacking. This study begins to fill that gap by creating a DNA reference library for Austrian dragonflies and damselflies. We collected many dragonfly and damselfly individuals from across Austria and sequenced two key DNA markers: COI, commonly used for species identification, and 16S, which is often used to detect species from environmental samples like water (a method known as eDNA metabarcoding). More than 90% of the samples were successfully identified using both markers. Some challenges appeared with closely related species, where the genetic differences are very small, but overall, the results show that both markers work well for identifying most species. This new reference DNA barcode library will support future biodiversity monitoring and conservation work, especially through non-invasive eDNA methods that help track species without needing to see or catch them.

Dragonflies and damselflies are important indicator species for quality and health of (semi-)aquatic habitats. Hitherto, 78 species of Odonata have been reported for Austria. Ecological data, Red List assessments, and a dragonfly association index exist, but population- and species-level genetic data are largely lacking. In this study, we establish a comprehensive reference DNA barcode library for Austrian dragonflies and damselflies based on the standard barcoding marker COI. Because of the increasing significance of environmental DNA (eDNA) analyses, we also sequenced a segment of the mitochondrial 16S rRNA gene, a marker often used in eDNA metabarcoding approaches. In total, we provide 786 new COI barcode sequences and 867 new 16S sequences for future applications. Sequencing success was >90 percent for both markers. Identification success was similar for both markers and exceeded 90 percent. Difficulties were only encountered in the genera Anax Leach, 1815, Chalcolestes Kennedy, 1920, Coenagrion Kirby, 1890 and Somatochlora Selys, 1871, with low interspecific genetic distances and, consequently, BIN (barcode index number) sharing. In Anax, however, individual sequences clustered together in species-specific groups in the COI tree. Irrespective of these challenges, the results suggest that both markers perform well within most odonate families in terms of sequencing success and species identification and can be used for reliably delimiting Austrian species, monitoring, and eDNA approaches.