Phylogenomics of the Neotropical fish family Serrasalmidae with a novel intrafamilial classification (Teleostei: Characiformes).

The Neotropical fish family Serrasalmidae comprises 16 extant genera and 101 species widespread through major Neotropical rivers with relevant importance for regional fisheries and aquaculture. The monophyly of Serrasalmidae and the recognition of three main clades are recurrent between morphological and molecular phylogenies. However, both intergeneric and interspecific relationships within each of those clades remain uncertain. Here, we used 81 terminals of 69 species (68%) and all 16 genera of Serrasalmidae to sequence 1553 loci of ultraconserved elements (UCEs), multiple nuclear loci widely applied in phylogenetic studies, and performed maximum likelihood, Bayesian, and species tree analyses. We obtained highly supported phylogenies in all applied methods corroborating the monophyly of Serrasalmidae and the three-clade hypotheses herein proposed as two subfamilies and two tribes: (Colossomatinae (Serrasalminae (Myleini + Serrasalmini))). Morphological features for each subfamily involve the absence (Colossomatinae) or presence (Serrasalminae) of a pre-dorsal spine. Morphological diagnoses among tribes include the pre-dorsal spine being continuous (Myleini) or discontinuous (Serrasalmini) relative to the first unbranched dorsal-fin ray. Our results highlight the complexity of the relationships especially the non-monophyly of Myleus, Mylesinus, Myloplus, Tometes, and Utiaritichthys within Myleini, as well as of Serrasalmus and Pristobrycon within Serrasalmini.

Molecular Data Reveal Multiple Lineages in Piranhas of the Genus Pygocentrus (Teleostei, Characiformes).

Carnivorous piranhas are distributed in four serrasalmid genera including Pygocentrus, which inhabit major river basins of South America. While P. cariba and P. piraya are endemics of the Orinoco and São Francisco basins, respectively, P. nattereri is widely distributed across the Amazonas, Essequibo, lower Paraná, Paraguay, and coastal rivers of northeastern Brazil, with recent records of introductions in Asia. Few studies have focused on the genetic diversity and systematics of Pygocentrus and the putative presence of additional species within P. nattereri has never been the subject of a detailed molecular study. Here we aimed to delimit species of Pygocentrus, test the phylogeographic structure of P. nattereri, and access the origin of introduced specimens of P. nattereri in Asia. Phylogenetic analyses based on a mitochondrial dataset involving maximum-likelihood tree reconstruction, genetic distances, Bayesian analysis, three delimitation approaches, and haplotype analysis corroborate the morphological hypothesis of the occurrence of three species of Pygocentrus. However, we provide here strong evidence that P. nattereri contains at least five phylogeographically-structured lineages in the Amazonas, Guaporé (type locality), Itapecuru, Paraná/Paraguay, and Tocantins/Araguaia river basins. We finally found that the introduced specimens in Asia consistently descend from the lineage of P. nattereri from the main Rio Amazonas. These results contribute to future research aimed to detect morphological variation that may occur in those genetic lineages of Pygocentrus.

Taxonomic revision of the Cis-Andean species of Mylossoma Eigenmann Kennedy, 1903 (Teleostei: Characiformes: Serrasalmidae).

A revision of the cis-Andean species of Mylossoma is presented. Four species were recognized: M. albiscopum and M. aureum from the rio Amazonas and rio Orinoco basins; M. duriventre, from the rio Paraguai, lower rio Paraná and rio Uruguai basins; and M. unimaculatum, an endemic species from the Tocantins-Araguaia system. Both Mylossoma albiscopum and M. unimaculatum were removed from the synonymy of Mylossoma duriventre, which had its occurrence range restricted to the La Plata basin. The recognition of these four valid species corroborates the results of a previous DNA barcode study. Redescriptions of each species, and an identification key for the genus are provided.

Molecular identification of cryptic diversity in species of cis-Andean Mylossoma (Characiformes: Serrasalmidae).

Mylossoma is a Serrasalmidae genus with only two current valid species in the cis-Andean region but with several available names, today considered as junior synonymous. Morphological information combined with single-locus DNA sequences of cytochrome c oxidase I gene analysed by Barcode Index Number and General Mixed Yule Coalescent model were used in the present study to help the recognition of Operational Taxonomic Units (OTUs) in cis-Andean Mylossoma and discuss species boundaries within the genus. Five OTUs were recognized based on both morphological and molecular approaches. The analysis using the Barcode Index Number resulted in five OTUs, with M. duriventre being split in one unity in the Amazon, one in the Orinoco, one in Paraná-Paraguay and one in Tocantins-Araguaia which is coherent with our morphological results.