Efficient Multiplexing of Pollinator Metabarcodes Using Oxford Nanopore MinION Sequencing: Insights for Meadow Management from Floral Environmental DNA

Many pollinating species are experiencing declines globally, making effective, fast, and portable pollinator monitoring methods more important than ever before. Pollinators can leave DNA on the flowers they visit, and metabarcoding of these environmental DNA (eDNA) traces provides an opportunity to detect the presence of flower visitors. This study introduces an efficient, cost-effective workflow for utilizing DNA barcoding to monitor biodiversity through environmental DNA (eDNA) left on flowers from pollinators, employing the portable MinION and Nanopore sequencing. The developed method employs multiplexing with dual molecular tags on universal cytochrome oxidase 1 (COI) barcode primers. We used this approach to compare the arthropod diversity present in three meadows with different vegetation at three time points during the flowering season. The utility of eDNA metabarcoding in investigating pollinator biodiversity and interactions is highlighted through our results, revealing the presence and interactions of 65 species from 30 families. We multiplexed individual eDNA samples from hundreds of flowers and found plant-pollinator dynamics that showed differences in species richness between sampling times and meadow diversity. Comparative analyses with conventional methods showed eDNA metabarcodings ability to identify diverse species and ecological interactions compared to field sampling. While some DNA likely came from eggs or microscopic insects difficult to remove from flowers, traces of eDNA from various arthropods on multiple plant species confirmed the methods applicability, promising robust ecological monitoring and research potential in the wake of global pollinator declines. This is the first reported use of MinION based nanopore sequencing to detect arthropod species from eDNA samples collected from flowers using the described affordable multiplexing method.