A revision of the cis-andean species of Brycon, with the exception of the Brycon pesu species-complex, is presented. Twenty-one Brycon species (including B. pesu) are recognized from cis-andean river systems: Brycon stolzmanni Steindachner, from the upper Río Marañon basin, Peru; Brycon coxeyi Fowler, from the Río Marañon basin, Ecuador and Peru; Brycon polylepis Moscó Morales, from the Lago de Maracaibo, Río Orinoco, upper rio Amazonas, and rio Tocantins basins, Venezuela, Colombia, Peru, and Brazil; Brycon coquenani Steindachner, from the upper Río Caroni, Río Orinoco basin, Venezuela; Brycon insignis Steindachner, from the rio Paraíba do Sul and small adjacent coastal river basins of eastern Brazil; Brycon vermelha Lima & Castro, endemic from the rio Mucuri basin, eastern Brazil; Brycon howesi new species, endemic from the rio Jequitinhonha basin, Brazil; Brycon dulcis new species, endemic from the rio Doce basin, eastern Brazil; Brycon ferox Steindachner, from several small coastal river systems, including the rio Mucuri basin in eastern Brazil; Brycon vonoi new species, from the rio Pardo basin and apparently also from a adjacent river system, the rio Una, in eastern Brazil; Brycon opalinus (Cuvier), from the headwaters of the rio Paraíba do Sul and rio Doce basins, eastern Brazil; Brycon nattereri Günther, from the headwaters of the upper rio Paraná, rio São Francisco, and upper rio Tocantins basins, Brazil; Brycon orthotaenia Günther, endemic from the rio São Francisco basin, Brazil; Brycon orbignyanus (Valenciennes), from the rio Paraná and rio Uruguai basins, Brazil, Paraguay, Argentina, and Uruguay; Brycon hilarii (Valenciennes), from the rio Paraguai, middle rio Paraná, and upper rio Amazonas basins, Brazil, Paraguay, Argentina, Peru, and Ecuador; Brycon whitei Myers & Weitzman, from the Río Orinoco basin in Colombia and Venezuela; Brycon amazonicus (Agassiz), from the Rio Amazonas and Río Orinoco basins, Brazil, Peru, Colombia, Bolivia, Venezuela, and Guyana; Brycon gouldingi Lima, endemic from the rio Tocantins basin, Brazil; Brycon melanopterus (Cope), from the western and central rio Amazonas basin, Brazil, Peru, Ecuador, and Colombia; and Brycon falcatus Müller & Troschel, widespread in the the rio Amazonas and Río Orinoco basins, and several guyanese river systems, in Brazil, Venezuela, Colombia, Peru, Bolivia, Guyana, Suriname, and French Guiana. All species are redescribed and illustrated, and a key to the species is provided. Comments on the diagnosis of the genus Brycon, the biogeography of the cis-andean species, and their current conservation status, are presented.

The upper rio Paraná basin drains the most developed and environmentally degraded region in South America: the Brazilian southeast. While it is one of the most well-known Neotropical fish assemblages, it is also one of the most threatened by anthropic activity. Urbanization, deforestation, dam construction, invasive species, and water pollution not only reduce the living area of species but also alter our perception of the basin and its biotic elements. Such changes are so profound and pervasive that raise uncertainties about the native or non-native status of several species. This paper aims to offer a detailed picture of the native diversity and historical biogeography of the fishes in the upper rio Paraná basin, which we hope will offer a solid foundation for future conservation policies. We update the list of native species, analyze geographical distributions, and identify biogeographical patterns, emphasizing areas requiring recognition as distinct biotas for conservation efforts. Over the past 15 years, more than 100 additional species have been described or recorded, expanding the total to 341 native species belonging to six orders and 30 families, making it the richest river basin in Brazil outside the Amazonian region. Unlike most neotropical basins where Characidae dominates, loricariids make up nearly one-fourth of the total fish diversity in the region. Species and clades concentrate in the central basin, while endemics are confined to peripheral areas due to the complex biogeographical history shared with neighboring basins. Eighteen distinct biogeographical regions are identified, discussing their composition, histories, and conservation implications. The upper rio Paraná basin has 10% of its fish fauna ranked as endangered and present 128 non-native species, including three hybrids. This places it as the major drainage with the largest number of endangered taxa in the neotropics and at the same time the one with the most numerous non-native elements. Existing protected areas are deemed ineffective in preserving diverse assemblages and fail to safeguard the majority of threatened and narrowly-endemic species.

Neotropical tetras of the family Characidae form the largest and most taxonomically complex clade within the order Characiformes. Previous phylogenetic relationships concur on the recognition of four major subclades, whereas knowledge on intergeneric and interspecific relationships remains largely incomplete or nonexistent. We sampled 575 specimens of 494 species and 123 genera classified in Characidae, generated new molecular data of ultraconserved elements (UCEs), and used likelihood and Bayesian analyses. The phylogeny (1348 UCE loci: 538 472 bp) yielded clades with unprecedented resolution at species- and genus-levels, allowing us to propose a new classification of former Characidae into four families: Spintherobolidae, Stevardiidae, Characidae, and Acestrorhamphidae. The family Stevardiidae includes nine subfamilies: Landoninae, Xenurobryconinae, Glandulocaudinae, Argopleurinae, Hemibryconinae, Stevardiinae, Planaltininae, Creagrutinae, and Diapominae. The family Characidae includes five subfamilies: Aphyocharacinae, Cheirodontinae, Exodontinae, Tetragonopterinae, and Characinae. The family Acestrorhamphidae congregates 15 subfamilies: Oxybryconinae, Trochilocharacinae, Stygichthyinae, Megalamphodinae, Stichonodontinae, unnamed subfamily, Stethaprioninae, Pristellinae, Jupiabinae, Tyttobryconinae, Hyphessobryconinae, Thayeriinae, Rhoadsiinae, Grundulinae, and Acestrorhamphinae. The phylogeny resolves intergeneric relationships and supports revalidation of Myxiops, Megalamphodus, Ramirezella, Holopristis, and Astyanacinus, synonymy of Aphyodite, Genycharax, and Psellogrammus, and expansion of Cyanogaster, Makunaima, Deuterodon, Hasemania, Hemigrammus, Bario, Ctenobrycon, and Psalidodon. The phylogeny opens avenues for new systematic reviews and redefinitions of included genera.

The analysis of the distribution patterns presented by examples of freshwater fishes restricted to headwater habitat: the anostomid Leporinus octomaculatus, the characins Jubiaba acanthogaster, Oligosarcus perdido, Moenkhausia cosmops, Knodus chapadae, Planaltina sp., the loricariid Hypostomus cochliodon, and the auchenipterid Centromochlus sp. provided evidences of a relatively recent shared history between the highlands of the upper rio Paraguay and adjoining upland drainage basins. Restricted to headwater of the uplands in the upper rio Paraguay and adjoining basins, these species provide biological evidence of the former extension of the central Brazilian plateau before the origin of the Pantanal Wetland. Disjunction took place due to an ecological barrier to these rheophilic taxa represented tectonic subsidence related to the origin of the Pantanal Wetland. Molecular analysis of Jubiaba acanthogaster revealed that the sample from the upper rio Xingu basin are the sister-group of a clade that includes samples from the upper rio Arinos (upper rio Tapajós) plus the upper rio Paraguay basin, supporting the assumption that the origin of the upper rio Paraguay basin causing vicariance between this basin and the upper rio Tapajós is the least vicariant event in the evolutionary history of the group.

Um levantamento preliminar da ictiofauna que ocorre na Estação Ecológica Serra Geral de Tocantins, situada no Sudeste do Estado do Tocantins e Noroeste do Estado da Bahia, é apresentado. A Estação Ecológica Serra Geral de Tocantins situa-se no divisor de águas entre as bacias do Rio São Francisco (Rio Sapão) e Rio Tocantins (bacias dos Rios Novo, Balsas e Manuel Alves). A cabeceira comum ou "água emendada" do Rio Sapão e Rio Galheiros, este um afluente do Rio Novo, situa-se no interior da estação e é considerada na literatura como uma possível área de intercâmbio ictiofaunístico entre a bacia do Rio São Francisco e a bacia do Rio Tocantins. Trinta e cinco espécies de peixes foram registradas dentro da Estação Ecológica Serra Geral de Tocantins e em seu entorno imediato, algumas delas desconhecidas da ciência e possivelmente endêmicas da região. Um total de 111 espécies de peixes foi registrado regionalmente (incluindo espécies de peixes registrados nos trechos do Rio Sapão e do Rio Novo/do Sono abaixo da estação). O acará Cichlasoma sanctifranciscense é aqui registrado pela primeira vez na bacia do Rio Tocantins. A ocorrência desta espécie, bem como do lambari Astyanax novae, no Rio Sapão e no Rio Novo/do Sono, são considerados os únicos exemplos inequívocos de transposição natural de espécies de peixes entre as bacias do Rio São Francisco e Tocantins efetuado pelas águas emendadas dos rios Sapão e Galheiros.