Vertebrate environmental DNA from understory leaf swabs unravel the canopy fauna of tropical forests
Abstract
The Amazon basin, one of the most biodiverse regions on Earth, remains underexplored despite its immense ecological importance. Arboreal species, which play critical ecological roles, are especially understudied due to the difficulties of accessing forest canopies. These knowledge gaps are particularly concerning as tropical ecosystems are experiencing unprecedented anthropogenic pressures. Addressing these challenges requires the development of efficient biomonitoring methods to uncover and preserve the Amazon's rich biodiversity.
I conducted an eDNA metabarcoding survey where I tested the viability of leaf swabbing, a new and innovative technique, for detecting arboreal and terrestrial vertebrates. Ninety leaves across five leaf types were swabbed across terra firme and várzea forests along the middle Juruá river, in the western Brazilian Amazon.
Twenty-eight species were detected from five taxonomic classes, with eight (28.6%) arboreal species detected. Várzea showed a significantly higher species detection rate per swab (14.68), compared to terra firme (7.64). However, the species turnover between the forests was extremely low (Jaccard dissimilarity index = 0.071). Forest type had a significant effect on read count, while leaf type and dimensions were non-significant.
While the leaf swabbing approach demonstrated its viability for detecting vertebrate terrestrial and arboreal taxa, it was limited by the low species richness detected in a highly biodiverse region. This limitation is likely attributed to incomplete reference databases and DNA degradation. These challenges reduce the method’s effectiveness in tropical forests. However, advancements in technology and expansion of reference databases could significantly improve this approach.