Cryptic species in the Neotropical fish genus Curimatopsis (Teleostei, Characiformes). -Zoologica Scripta, 00, 000-000. Detritivores of the fish family Curimatidae are assigned to eight genera, one of which, the Curimatopsis, with only five species, is the least speciose genus and sister to other seven genera in the family. Ongoing morphological investigations reveal, however, the likely existence of additional species. In this study, fifty-one specimens of Curimatopsis from multiple rivers of the Amazon, Paraguay and Suriname drainages were identified morphologically according to the present species concepts and then barcoded using the universal cytochrome c oxidase subunit I (COI) mitochondrial marker. Species delimitation analyses were conducted using Bayesian methods through the general mixed Yule-coalescent analysis combined with conventional likelihood, genetic distance and haplotypic diversity approaches. We found eleven well-supported clusters that represent four of the named species and seven cryptic, undescribed species of Curimatopsis. Our results show a clear delimitation of species boundaries constrained by distinct Amazonian river ecotones that may have promoted intrageneric lineage diversification. This is the first of a series of genetic studies applicable to future taxonomic, phylogenetic and evolutionary studies across the Curimatidae.

The Neotropics harbor the most species-rich freshwater fish fauna on the planet, but the timing of that exceptional diversification remains unclear. Did the Neotropics accumulate species steadily throughout their long history, or attain their remarkable diversity recently? Biologists have long debated the relative support for these museum and cradle hypotheses, but few phylogenies of megadiverse tropical clades have included sufficient taxa to distinguish between them. We used 1,288 ultraconserved element loci (UCE) spanning 293 species, 211 genera and 21 families of characoid fishes to reconstruct a new, fossil-calibrated phylogeny and infer the most likely diversification scenario for a clade that includes a third of Neotropical fish diversity. This phylogeny implies paraphyly of the traditional delimitation of Characiformes because it resolves the largely Neotropical Characoidei as the sister lineage of Siluriformes (catfishes), rather than the African Citharinodei. Time-calibrated phylogenies indicate an ancient origin of major characoid lineages and reveal a much more recent emergence of most characoid species. Diversification rate analyses infer increased speciation and decreased extinction rates during the Oligocene at around 30 million years ago (Ma) during a period of mega-wetland formation in the proto-Orinoco-Amazonas. Three species-rich and ecomorphologically diverse lineages (Anostomidae, Serrasalmidae, and Characidae) that originated more than 60 Ma in the Paleocene experienced particularly notable bursts of Oligocene diversification and now account collectively for 68% of the approximately 2,150 species of Characoidei. In addition to paleogeographic changes, we discuss potential accelerants of diversification in these three lineages. While the Neotropics accumulated a museum of ecomorphologically diverse characoid lineages long ago, this geologically dynamic region also cradled a much more recent birth of remarkable species-level diversity.

Migratory detritivores of the characiform family Prochilodontidae occur throughout the freshwaters of much of South America. Prochilodontids often form massive populations and many species achieve substantial body sizes; a combination that makes them one of the most commercially important fish groups on the continent. Their economic significance notwithstanding, prochilodontids have never been the subject of a comprehensive molecular phylogenetic analysis. Using three mitochondrial and three nuclear loci spanning all prochilodontid species, we generated a novel phylogenetic hypothesis for the family. Our results strongly support monophyly of the family and the three included genera. A novel, highly supported placement of Ichthyoelephas sister to the clade containing Prochilodus and Semaprochilodus diverges from a previous morphological hypothesis. Most previously hypothesized interspecific relationships are corroborated and some longstanding polytomies within Prochilodus and Semaprochilodus are resolved. The morphologically similar P. brevis, P. lacustris, P. nigricans and P. rubrotaeniatus are embedded within what is herein designated as the P. nigricans group. Species limits and distributions of these species are problematic and the group clearly merits taxonomic revision.

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A new species of Tetragonopterus Cuvier, 1816 (Characiformes: Characidae: Tetragonopterinae) from the rio Jari, Amapá, northern Brazil Bruno F. Melo, Ricardo C. Benine, Tatiane C. Mariguela and Claudio Oliveira A new species of Tetragonopterus is described from the rio Jari, a tributary to the left margin of rio Amazonas, at the border between Amapá and Pará States, northern Brazil. It is morphologically diagnosed from the other species of the genus (T. argenteus, T. chalceus, and T. rarus new combination) by the lozenge-shaped spot on the caudal peduncle vs. rounded to square spot on the other species. Partial sequences of the mitochondrial gene Cytochrome Oxidase C subunit I, from representatives of all valid species of Tetragonopterus, including this new species, were analyzed. The obtained results revealed a significant genetic distance between the new species and its congeners. A discussion on the new combination, Tetragonopterus rarus, is also provided. Uma espécie nova de Tetragonopterus é descrita do rio Jari, um tributário da margem esquerda do rio Amazonas, na divisa entre os Estados do Amapá e Pará, norte do Brasil. Esta é morfologicamente diferenciada das outras espécies do gênero (T. argenteus, T. chalceus e T. rarus combinação nova) pelo formato losangular da mancha no pedúnculo caudal contra uma mancha arredondada a quadrangular nas demais espécies. Sequências parciais do gene mitocondrial citocromo oxidase C subunidade I de representantes de todas as espécies válidas de Tetragonopterus, incluindo esta espécie nova, foram analisadas. Os resultados obtidos revelaram uma significante distância genética entre esta espécie nova e as demais do gênero. É apresentada uma discussão sobre a nova combinação, Tetragonopterus rarus.

The family Trichomycteridae is one of the most diverse groups of freshwater catfishes in South and Central America with eight subfamilies, 41 genera and more than 300 valid species. Its members are widely distributed throughout South America, reaching Costa Rica in Central America and are recognized by extraordinary anatomical specializations and trophic diversity. In order to assess the phylogenetic relationships of Trichomycteridae, we collected sequence data from ultraconserved elements (UCEs) of the genome from 141 specimens of Trichomycteridae and 12 outgroup species. We used a concatenated matrix to assess the phylogenetic relationships by Bayesian inference (BI) and maximum likelihood (ML) searches and a coalescent analysis of species trees. The results show a highly resolved phylogeny with broad agreement among the three distinct analyses, providing overwhelming support for the monophyletic status of subfamily Trichomycterinae including Ituglanis and Scleronema. Previous relationship hypotheses among subfamilies are strongly corroborated, such as the sister relationship between Copionodontinae and Trichogeninae forming a sister clade to the remaining trichomycterids and the intrafamilial clade TSVSG (Tridentinae-Stegophilinae-Vandelliinae-Sarcoglanidinae-Glanapteryginae). Monophyly of Glanapteryginae and Sarcoglanidinae was not supported and the enigmatic Potamoglanis is placed outside tridentinae. Unraveling the relationships of major sections of the Tree of Life is one of the most daunting challenges of the evolutionary biology. Massively parallel DNA sequencing (so-called Next-gen sequencing) is a promising tool that is helping to resolve the interrelationships of longstanding problematic taxa 1-4. One of the most common classes of phylogenomic methods involves the sequence capture of nuclear regions in the flanks and cores of the ultraconserved elements (UCEs) 2. The more variable flanking UCE regions allow a better resolution of nodes across a broad range of evolutionary timescales in a given phylogeny 2. As variation in the flanks increases with distance from the core UCE, this combined approach displays a balance between having a high enough substitution rate while minimizing saturation, thus providing information for estimating phylogenies at multiple evolutionary timescales 2,3. Recent studies of actinopterygians 5 , flatfishes 6 , cichlids 7 , ostariophysan 8 , acanthomorphs 9 , Loricariidae 10 , knifefishes 11 , among other vertebrates groups 3,12 , have shown that UCEs are excellent markers for phylogenetic studies because of their ubiquity among taxonomic groups 13 , low degrees of paralogy 14 , and low saturation 3. According to Gilbert et al. 15 , the phylogenetic informativeness of the combined flank and core regions of UCEs outperfoms protein-coding genes used in multilocus studies. Additionally, phylogenomic approaches are characterized by their potential to collect data from at least one order of magnitude more loci than the traditional sequencing techniques applied to protein-coding le...

No abstract

Evidence that migration prevents population structure among Neotropical characiform fishes has been reported recently but the effects upon species diversification remain unclear. Migratory species of Prochilodus have complex species boundaries and intrincate taxonomy representing a good model to address such questions. Here, we analyzed 147 specimens through barcode sequences covering all species of Prochilodus across a broad geographic area of South America. Species delimitation and population genetic methods revealed very little genetic divergence among mitochondrial lineages suggesting that extensive gene flow resulted likely from the highly migratory behavior, natural hybridization or recent radiation prevent accumulation of genetic disparity among lineages. Our results clearly delimit eight genetic lineages in which four of them contain a single species and four contain more than one morphologically problematic taxon including a trans-Andean species pair and species of the P. nigricans group. Information about biogeographic distribution of haplotypes presented here might contribute to further research on the population genetics and taxonomy of Prochilodus.