Drops of Diversity: Vertebrate rainwash eDNA metabarcoding in an Amazonian floodplain forest

Abstract

Extensive research has been conducted along the Medio Juruá River in the western Brazilian Amazon, with vertebrate species being relatively well-documented. However, studies on biodiversity in this region has predominantly relied on traditional monitoring methods, and the potential use of environmental DNA (eDNA) based approaches remain largely unexplored. This study focused on eDNA metabarcoding, comparing active and passive rainwash filtering to detect vertebrate species, particularly arboreal taxa, on the Medio Juruá River floodplain during the low-water season. Three rainwash events were recorded. To amplify vertebrate eDNA, the Riaz 12S and Leray (COI) primer sets were used. The Leray (COI) primer found only two species, whereas Rias 12S detected a total of 45 species across four classes. The active filtering method found significantly more vertebrate species (p = 0.00386), but for exclusively arboreal species, no statistical significance between methods was found. Contrary to expectations, no amphibians and only one reptile wasdetected. Interestingly, this study detected the rare species bush dog (Speothos venaticus), highlighting the method’s potential use for rare species detection. This study demonstrates the potential of rainwash eDNA in the Amazon floodplains as a minimally invasive biodiversity monitoring tool, but further refinements is required to improve detection rates.