Tails of Biodiversity: Vertebrate Community Assessment in a Neotropical River Basin via <scp>eDNA</scp> Metabarcoding

ABSTRACT Located in the southeast of Brazil, the Rio Santo Antônio basin, a tributary of the Rio Doce basin, has many preserved remnants of the Atlantic Forest, but is otherwise under imminent threats from several land use stressors. In this study, we used environmental DNA (eDNA) metabarcoding to assess vertebrate diversity in the headwaters of the Rio Santo Antônio basin, aiming to elucidate key ecological factors influencing its vertebrate richness. Additionally, we provide the first vertebrate species inventory for the basin. In 2023, water samples from 15 third‐ and fourth‐order streams were collected and metabarcoding assays targeting the mitochondrial 12S rRNA gene were employed to detect the vertebrate community. We identified 119 vertebrate taxonomic units distributed across two distinct communities: one on the eastern slope and another on the western slope of the basin, both influenced by large‐scale mining activities. We demonstrated that vertebrate richness was not correlated with forest cover or pH but was strongly associated with the water's oxidation–reduction potential (ORP). We interpret ORP as a reflection of local conditions, where sites with higher ORP values also exhibited greater taxonomic richness and were related to greater forest cover, lower air and water temperatures, and greater distance from mining activity. The vertebrate biodiversity and biogeographic distribution described here highlight the value of eDNA metabarcoding as a monitoring approach and support decision‐making and conservation efforts aimed at preserving the remaining Atlantic Forest in the headwaters of the Rio Santo Antônio basin.