Hidden Diversity Hampers Conservation Efforts in a Highly Impacted Neotropical River System

Abstract

Neotropical Rivers host a highly diverse ichthyofauna, but taxonomic uncertainty prevents appropriate conservation measures. The Doce River Basin (DRB), lying within two Brazilian threatened hotspots (Atlantic Forest and Brazilian Savanna) in south-east Brazil, faced the worst ever environmental accident reported for South American catchments, due to a dam collapse that spread toxic mining tailings along the course of its main river. Its ichthyofauna was known to comprise 71 native freshwater fish species, of which 13 endemic. Here, we build a DNA barcode library for the DRB ichthyofauna, using samples obtained before the 2015 mining disaster, in order to provide a more robust biodiversity record for this basin, as a baseline for future management actions. Throughout the whole DRB, we obtained a total of 306 barcodes, assigned to 69 putative species (with a mean of 4.54 barcodes per species), belonging to 45 genera, 18 families, and 5 orders. Average genetic distances within species, genus, and families were 2.59, 11.4, and 20.5%, respectively. The 69 species identified represent over 76% of the known DRB ichthyofauna, comprising 43 native (five endemic, of which three threatened by extinction), 13 already known introduced species, and 13 unknown species (such as Characidium sp., Neoplecostomus sp., and specimens identified only at the sub-family level Neoplecostominae, according to morphological identification provided by the museum collections). Over one fifth of all analyzed species (N = 16) had a mean intraspecific genetic divergence higher than 2%. An integrative approach, combining NND (nearest neighbor distance), BIN (barcode index number), ABGD (automatic barcode gap discovery), and bPTP (Bayesian Poisson Tree Processes model) analyses, suggested the occurrence of potential cryptic species, species complex, or historical errors in morphological identification. The evidence presented calls for a more robust, DNA-assisted cataloging of biodiversity-rich ecosystems, in order to enable effective monitoring and informed actions to preserve and restore these delicate habitats.

Influence of preservation methods, sample medium and sampling time on eDNA recovery in a neotropical river

“…Neotropical freshwaters harbor high, and often understudied (Sales, Mariani, Salvador, Pessali, & Carvalho, 2018), biodiversity and eDNA could assist biodiversity assessment and monitoring programs, with the ultimate aim to contribute to conservation and management strategies. Higher temperatures and solar radiation associated with increased turbidity in tropical waters might contribute to make rivers in the tropics a challenge for eDNA studies due to possibly higher degradation rates (Barnes et al, 2014; Matheson, Gurney, Esau, & Lehto, 2014; Pilliod et al, 2014).…”

DNA barcoding reveals cryptic diversity in the underestimated genus Triplophysa (Cypriniformes: Cobitidae, Nemacheilinae) from the northeastern Qinghai-Tibet Plateau

“…Moreover, DNA barcodes have been used to construct barcode databases, such as the Barcode of Life Data Systems (BOLD) (https ://www.bolds ystem s.org), which barcoded approximately 96,425 fish specimens belonging to 10,267 species. DNA barcoding can complement traditional species identification as a method of automating and standardizing the process of specimen identification, thereby reducing the dependence on the experience of taxonomists [8,63].…”

A new species of Trichomycterus Valenciennes 1832 (Trichomycteridae: Siluriformes) from the Rio Doce drainage with remarkable similarities with Bullockia and a CT‐scan survey

“…The Rio Doce seems to be one of the hotspots of endemic freshwater fish diversity in Southeastern Brazil, with its known biodiversity constantly increasing (Barros et al, ; Sales et al, ). The basin has suffered tremendous environmental destruction in recent years, mainly from mining disasters, deforestation, and dam building; and much of its main course has been heavily impacted.…”