One thousand DNA barcodes of piranhas and pacus reveal geographic structure and unrecognised diversity in the Amazon

Abstract

Piranhas and pacus (Characiformes: Serrasalmidae) are a charismatic but understudied family of Neotropical fishes. Here, we analyse a DNA barcode dataset comprising 1,122 specimens, 69 species, 16 genera, 208 localities, and 34 major river drainages in order to make an inventory of diversity and to highlight taxa and biogeographic areas worthy of further sampling effort and conservation protection. Using four methods of species discovery—incorporating both tree and distance based techniques—we report between 76 and 99 species-like clusters, i.e. between 20% and 33% of a priori identified taxonomic species were represented by more than one mtDNA lineage. There was a high degree of congruence between clusters, with 60% supported by three or four methods. Pacus of the genus Myloplus exhibited the most intraspecific variation, with six of the 13 species sampled found to have multiple lineages. Conversely, piranhas of the Serrasalmus rhombeus group proved difficult to delimit with these methods due to genetic similarity and polyphyly. Overall, our results recognise substantially underestimated diversity in the serrasalmids, and emphasise the Guiana and Brazilian Shield rivers as biogeographically important areas with multiple cases of across-shield and within-shield diversifications. We additionally highlight the distinctiveness and complex phylogeographic history of rheophilic taxa in particular, and suggest multiple colonisations of these habitats by different serrasalmid lineages.

Molecular characterization and genetic relationships of seven piranha species of the genera Serrasalmus and Pygocentrus (Characiformes: Serrasalmidae) from Paraná-Paraguay, São Francisco and Tocantins River basins in Brazil

“…Evolutionary relationships among species of piranhas have been the subject of several publications with morphological (Machado-Allison, 1983), cytological (Nakayama et al, 2002(Nakayama et al, , 2012, parasitological (Van Every and Kritsky, 1992) and molecular markers (Ortí et al, 1996(Ortí et al, , 2008Freeman et al, 2007;Hubert et al, 2007;Thompson et al, 2014;Machado et al, 2018;Mateussi et al, 2019). Morphological and molecular approaches agree with the hypothesis that the genera of piranhas Pygopristis, Pygocentrus, Pristobrycon and Serrasalmus together with Catoprion, represent a monophyletic unit of the family Serrasalmidae.…”

“…The high values of genetic distance and the differentiation of S. maculatus haplogroups from Tocantins and Paraná-Paraguay River basins, associated with the non-monophyletic condition of S. maculatus observed in the dendrograms, may constitute evidence for more than one species within S. maculatus (Bignotto et al, 2019). Similarly, Machado et al (2018) did not recover the monophyletic condition of the species.…”

A new species of Piaractus (Characiformes: Serrasalmidae) from the Orinoco Basin with a redescription of Piaractus brachypomus

“…() and Machado et al . () P. mesopotamicus is phylogenetically nested within P. brachypomus (Figure ). In spite of a lack of reciprocal monophyly of P. mesopotamicus and P. brachypomus , we consider P. mesopotamicus to be a valid species, albeit one that would benefit from additional taxonomic and phylogenetic analyses.…”

Genetic evidence for a species complex within the piranha Serrasalmus maculatus (Characiformes, Serrasalmidae) from three Neotropical river basins based on mitochondrial DNA sequences

“…The difference between S. maculatus populations of the Upper Paraguay River and Upper Paraná River was observed both at cytogenetic (Cestari and Galetti Jr, 1992) and molecular levels (present study). Additionally, Machado et al (2018) refuted the monophyly of S. maculatus and reported that the population of S. maculatus from the upper Paraná River formed a distinct lineage from the population of the lower Paraná River. Similarly, in the present study, the two populations were genetically differentiated from each other; nevertheless, with relatively low values.…”