Elusive tropical forest canopy diversity revealed through environmental DNA contained in rainwater

Exploring the biodiversity hidden in tropical rainforests canopies represents a major frontier in biodiversity research yet remains challenging. Environmental DNA (eDNA) can revolutionize this field as it did already in various ecosystems. Here, we test the hypothesis that eDNA contained in canopy throughfall could be used to monitor this elusive diversity and detect anthropogenic disturbance. Using custom-made, low-cost rain collectors, we sampled rainwash eDNA in a mature Amazonian forest and a nearby tree plantation. We successfully detected eDNA from tropical woody and epiphyte plants, vertebrates (mammals, birds, and amphibians), and insects (e.g., mosquitoes, ants, and beetles). The taxonomic composition and diversity reflected disturbance, with significantly lower diversity in the plantation. Crucially, rainwash eDNA integrated biodiversity over a 10-day period in passive collectors and provided a local signature. This approach has thus potential for establishing a cost-effective monitoring system for tropical moist forest canopies, applicable in impact assessments and sustainable management.