Monitoring the birds and the bees: Environmental DNA metabarcoding of flowers detects plant–animal interactions

Animal pollinators are vital for the reproduction of ~90% of flowering
plants. However, many of these pollinating species are experiencing
declines globally, making effective 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. Our study,
collecting flowers from seven plant species with diverse floral
morphologies, for eDNA metabarcoding analysis, illustrated the value of
this novel survey tool. eDNA metabarcoding using three assays, including
one developed in this study to target common bush birds, recorded more
animal species visiting flowers than visual surveys conducted
concurrently, including birds, bees, and other species. We also recorded
the presence of a flower visit from a western pygmy possum; to our
knowledge, this is the first eDNA metabarcoding study to simultaneously
identify the interaction of insect, mammal, and bird species with flowers.
The highest diversity of taxa was detected on large inflorescence flower
types found on Banksia arborea and Grevillea georgeana. The study
demonstrates that the ease of sample collection and the robustness of the
metabarcoding methodology have profound implications for future management
of biodiversity, allowing us to monitor both plants and their attendant
cohort of potential pollinators. This opens avenues for rapid and
efficient comparison of biodiversity and ecosystem health between
different sites and may provide insights into surrogate pollinators in the
event of pollinator declines.