DNA barcoding analysis of Gymnotus species in two Neotropical river basins

Abstract

Gymnotus is the most species rich genus of electric fish in the Neotropical region. Recently, a previously unknown diversity has been found in this genus, motivating a pursuit for new species. In this study, a fragment of the mitochondrial Cytochrome c Oxidase subunit I (COI) gene was used to analyze the diversity of 10 morphospecies of Gymnotus (G. carapo, G. pantanal, G. sylvius, G. ineaquilabiatus, G. pantherinus, G. coropinae, G. jonasi, G. cylindricus, G. chaviro, G. tigre) in two Neotropical river basins (Paraná River and Doce River), in addition to specimens identified as Gymnotus sp. At least 15 OTUs were determined, eight of which belonged to the carapo complex. Our results indicate the existence of at least four Gymnotus species belonging to the carapo clade in the upper Paraná River basin and possibly erroneous previous identifications. Besides that, we identified a possible new species of Gymnotus in the Rio Doce basin. The Generalized Mixed Yule Coalescent (GMYC) and Poisson Tree Processes (PTP) molecular delimitation approaches place other specimens found in the upper Paraná River and Guaíba River (Gymnotus sp.) in well-established groups that should be considered in studies involving the carapo complex.