Preserving insects for non destructive metabarcoding

Suspended traps such as Lindgren funnel traps and vane traps are increasingly used in combination with DNA metabarcoding to characterise canopy arthropod communities. Despite their wide use, it remains unclear how different preservatives and storage conditions affect DNA integrity in samples destined for molecular analysis. Ethanol, while commonly used as a preservative, poses several challenges for field deployment: it is volatile, expensive, and unsuitable for passive trapping because it is known to attract some insects. Monopropylene glycol (MPG) has emerged as a practical alternative: it is non-toxic, affordable, easy to handle and transport, and preserves specimen morphology for identification. However, its effect on DNA preservation, especially when diluted by rainwater in the field or during storage, remains poorly understood. This study uses insect mock communities of low (6 species) and high (12 species) diversity to test the effects of preservative type, storage duration, and ethanol transfer on species detection via non-destructive DNA metabarcoding. Mock communities were stored in ethanol, MPG, or diluted MPG (DMPG) and processed with metabarcoding over time. Community composition recovered was significantly influenced by preservative type and the diversity of the mock community. On the other hand, the effects of storage time and transfer were significant only in low diversity mock communities, and detection rates varied across species. Overall, results confirmed that MPG is a suitable and effective fixative for short- to medium-term storage at 5°C, even when diluted, maintaining DNA integrity for metabarcoding applications. These findings are consistent with prior studies and provide further support for MPG as a viable alternative to ethanol in arthropod biomonitoring and research.