No abstract

Mitochondrial molecular markers (DNA sequences of D-loop, cytochrome b and cytochrome c oxidase I) were employed to characterize populations of the piranha Serrasalmus maculatus from Upper Paraná, Upper Paraguay and Tocantins River basins. D-loop sequences of S. maculatus population from Paraná-Paraguay River basin exhibited tandem repeats of short motifs (12 base pairs) and variable numbers depending on specimens, accounting for length variation. Concatenated mitochondrial sequences suggested that S. maculatus encompasses different mitochondrial DNA lineages. Although sampling was restricted to three river basins, phylogenetic analysis clearly indicated that the species currently recognized as S. maculatus presents high genetic variability. Maximum likelihood and Bayesian analysis clustered S. maculatus populations according to their locations. However, the highest genetic differentiation was identified between populations from Paraná-Paraguay system and Tocantins River basin. Three species delimitation analyses (PTP, GMYC, and ABGD) suggested that there are at least two species among the analyzed populations. The analysis of the mitochondrial sequences evidenced genetic differentiation among populations corresponding to related, but different species, suggesting that at least S. maculatus from the Tocantins River and Paraná-Paraguay River basins are most likely different species. Therefore, S. maculatus should be considered a species complex with morphologically cryptic diversity. An integrative revision is suggested.

ABSTRACT. Astyanax altiparanae, belonging to the bimaculatus group, which includes species with similar colors and morphology, occurs in the upper Paraná River basin. As the use of mitochondrial DNA has made great strides in the diagnosis of species, in previous researches, two strains were detected in A. altiparanae with a high divergence in the D-loop region, provisionally called AltoPR and AltoPR-D. Evidence led to the hypothesis that the two strains did not belong to the same species. Phylogenetic hypotheses were produced by maximum-likelihood. Mean internal distances of the AltoPR and AltoPR-D groups were respectively 0.002 and 0.003, with the distance between them being 0.037. Sequences from GenBank of specimens collected from the Paraíba do Sul River basin were also divided into two groups, of which one may be identified as AltoPR. Since the other group provided an intermediate distance when compared to AltoPR-D, an in-depth investigation was required. The other species analyzed showed a greater distance and was revealed to be a monophyletic taxon. The results suggested that they are really two species and that neither corresponds to the other species used in the current study.

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. K E Y W O R D S

The distribution of Phalloceros species is generally allopatric and restricted; however, Phalloceros harpagos has a wide distribution and exhibits morphological variation among populations from different Brazilian river basins. Different species delimitation tests using cytochrome C oxidase subunit I gene sequences indicated that P. harpagos is a species complex that comprises between 7 and 9 phylogroups. The separation of the Paraná and Paraíba do Sul River basins most likely caused the diversification of these phylogroups in the Miocene period. The majority of phylogroups have a narrow distribution; however, one phylogroup has a broad distribution, being found primarily in the Paraná, Ribeira de Iguape, and Iguaçu River basins. This distribution can be attributed to possible headwater capture events caused by the reactivation of faults and erosion in the quaternary. Estimates about the times of divergence based on molecular data could be used to infer the biogeographic processes related to the diversification of South American freshwater fish.