Abstract
With an estimate of around 9,000 species, the Neotropical region hosts the greatest diversity of freshwater fishes of the world. Genetic surveys have the potential to unravel isolated and unique lineages and may result in the identification of undescribed species, accelerating the cataloguing of extant biodiversity. In this paper, molecular diversity within the valuable and widespread Neotropical genus Hoplias was assessed by means of DNA Barcoding. The geographic coverage spanned 40 degrees of latitude from French Guiana to Argentina. Our analyses revealed 22 mitochondrial lineages fully supported by means of Barcode Index Number, Automatic Barcode Gap Discovery and phylogenetic analyses. This mtDNA survey revealed the existence of 15 fully supported mitochondrial lineages within the once considered to be the continentally distributed H. malabaricus. Only four of them are currently described as valid species however, leaving 11 mitochondrial lineages currently “masked” within this species complex. Mean genetic divergence was 13.1%. Barcoding gap analysis discriminated 20 out of the 22 lineages tested. Phylogenetic analyses showed that all taxonomically recognized species form monophyletic groups. Hoplias malabaricus sensu stricto clustered within a large clade, excluding the representatives of the La Plata River Basin. In the H. lacerdae group, all species but H. curupira showed a cohesive match between taxonomic and molecular identification. Two different genetic lineages were recovered for H. aimara. Given the unexpected hidden mitochondrial diversity within H. malabaricus, the COI sequence composition of specimens from Suriname (the type locality), identified as H. malabaricus sensu stricto, is of major importance.
Highlights
The Neotropical region hosts the greatest diversity of freshwater fishes in the world [1]
To gain further consensus among different methodologies in delimitations of Operational Taxonomic Units (OTUs), we explored whether groups identified by the Barcode Index Number (BIN) and Automatic Barcode Gap Discovery method (ABGD) approaches were supported by reciprocal monophyly in a Bayesian phylogenetic analysis
Among 73 analysed specimens of Hoplias from La Plata River Basin, 61 specimens were identified as belonging to the H. malabaricus group [H. misionera (n = 38), H. mbigua (n = 5) and H. argentinensis (n = 18)] and 12 to the H. lacerdae group [H. lacerdae (n = 5) and H. australis (n = 7)]
Summary
The Neotropical region hosts the greatest diversity of freshwater fishes in the world [1]. Cryptic species undergoing radiation without morphological changes are not detected by traditional taxonomy, and the existence of genetically different entities within a supposed unique nominal taxon has been reported many times during the last decades [5]. DNA Barcoding has proved to be an important tool to detect cryptic diversity [7,8,9,10,11] and to flag potential undescribed taxa [12]. Some authors have already detected cryptic species and described new ones using an integrative approach combining DNA Barcoding and traditional taxonomy [13,14,15,16,17,18,19,20]. Application of DNA barcoding has effectively facilitated species identification of unknown samples for conservation purposes [21]
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