DNA barcoding confirms the occurrence of Rhamdia branneri and Rhamdia voulezi (Siluriformes: Heptapteridae) in the Iguaçu River Basin

Abstract

DNA barcoding is a widely utilized molecular-based identification of species and taxonomic resolutions. Until recently, Rhamdia voulezi and Rhamdia branneri were considered species synonyms of Rhamdia quelen; however, morphological and cytogenetic analyses have suggested the validity of distinct species. Due to the absence of molecular taxonomy of R. voulezi and R. branneri, the objective of this study was to test its validity through traditional DNA barcoding and the GMYC (General Mixed Yule Coalescent) COI-based analyses in 19 specimens from the Iguaçu River Basin. In both methodologies, three MOTUs (Molecular Operational Taxonomic Units) were identified based on the estimated optimum threshold (OT = 0.77). The average inter-MOTU distance (NJ, K2P) between R. branneri and R. voulezi was 1.4%, and 0% intra-MOTU distance in both species. The two species identified as R. branneri and R. voulezi showed correspondence with taxonomic and morphological identifications. With regard to R. quelen, the average intra-MOTU distance was greater than OT (2.7%), indicating that this species can be formed by different MOTUs. We suggest that molecular and taxonomic studies should be employed concurrently in R. quelen, to prevent contamination of wild species by hybridizations. O DNA barcoding é uma ferramenta molecular precisa para a identificação de espécies e resoluções taxonômicas. Até recentemente, Rhamdia voulezi e Rhamdia branneri eram consideradas sinônimas de Rhamdia quelen, contudo caracteres morfológicos e citogenéticos têm apontado à validade de ambas. Devido à escassez de informações sobre a taxonomia molecular de R. voulezi e R. branneri, o objetivo do presente estudo foi testar a validade das mesmas através do método de DNA barcoding tradicional e GMYC (General Mixed Yule Coalescent), por meio da análise do gene COI em 19 espécimes do rio Iguaçu. Em ambos os métodos, três MOTUs (Unidades Taxonômicas Operacionais Moleculares) foram identificadas com base no ótimo threshold (OT = 0,77). A média inter-MOTU (NJ, K2P) entre R. branneri e R. voulezi foi 1,4%, com valores de 0% intra-MOTUs em ambas espécies. As duas espécies identificadas como R. voulezi e R. branneri apresentaram correspondência com a identificação taxonômica e morfológica dos respectivos vouchers. No que se refere a R. quelen, os resultados intra-MOTU foram superiores ao OT (2,7%), evidenciando a possibilidade de existirem diferentes MOTUs denominadas como R. quelen. Sugerimos que estudos moleculares e taxonômicos sejam empregados em R. quelen, para evitar a contaminação de espécies selvagens por hibridizações.Palavras-chave: Aquicultura, COI, Complexo de espécies, Jundiá, MOTU.

DNA barcoding reveals blend of silver catfishRhamdiaspecies from fish farms in Southern Brazil

“…Despite the overlap of some individuals, most divergence values among the MOTUs were high (mean 3.5% and maximum 5.1%), corroborating the results observed by Ribolli et al. (). In addition, the absence of the barcode gap also indicates the presence of cryptic species, which is supported by previous studies that suggested that R. quelen is a complex of species (Perdices et al., ; Ríos, Bouza, Gutiérrez & García, ).…”

“…The DNA barcoding analysis supports the presence of at least three distinct species cultivated and commercialized as “jundiá” in southern Brazil. The interspecific genetic distance was high (1.1%–5.1%), and this distance is above the optimum threshold estimated for the genus Rhamdia (0.77%; Ribolli et al., ). Despite the presence of high intraspecific values in the three species studied, the dataset showed no barcode gap (an overlap of the intraspecific and interspecific values used to delimit species).…”

“…However, the ability to identify pure and hybrid lineages is essential to the improvement, management and conservation of native species (Allendorf, Leary, Spruell & Wenburg, ). Despite the great relevance of “jundiá” for aquaculture, the current taxonomic classification of R. quelen is confusing and likely represents a complex of species (Ribolli et al., ; Ríos et al., ).…”

“…The runs were combined using the LogCombiner v.1.8.3 (Drummond, Suchard, Xie & Rambaut, ) with a burn‐in of 25%, which is the method recommended by Machado, Ishizuka, Freitas, Valiati and Galetti (). We adopted an optimal threshold (OT) of 0.77%, which was previously proposed for the delimitation of R. branneri and R. voulezi (Ribolli et al., ), as the limit between intraspecific and interspecific distances.…”

“…In all, 49 of these species were synonymized as Rhamdia quelen (Reis, Kullander & Ferraris, 2003), and mtDNA analyses identified R. laticauda and R. guatemalensis as species found in Central America and suggested that R. quelen is a sister group widespread in South America (Perdices, Bermingham, Montilla & Doadrio, 2002). Two other R. quelen synonyms (Rhamdia branneri and Rhamdia voulezi) were recently confirmed as valid species through morphological and molecular studies (Garavello & Shibatta, 2016;Ribolli, Scaranto, Shibatta, Bombardelli & Zaniboni-Filho, 2017). The delimitation of individual species among all other synonyms of cis-Andean Rhamdia species using morphological and molecular approaches is limited.…”