RESUMO A ictiofauna do sistema hidrográfico La Plata é dividida em alto e baixo rio Paraná devido ao isolamento geográfico dos Saltos das Sete Quedas há 22 milhões de anos, atualmente inundado pelo lago da represa da Usina de Itaipu. Em Parodontidae, espécies pares ou grupos de espécies crípticas foram descritos entre esses sistemas. Contudo, embora o isolamento genético e especiação já tenham sido propostos em outras espécies do grupo, Parodon nasus tem sido mantido como espécie válida e distribuída em toda a bacia do rio La Plata. Nessa perspectiva, exemplares de P. nasus de quatro diferentes pontos de amostragem nos sistemas do alto e baixo rio Paraná foram comparados quanto ao arranjo dos cariótipos, análises moleculares de biologia populacional e delimitação de espécies, afim de investigar seu isolamento genético e populacional na bacia do rio La Plata. Apesar da barreira geográfica e imensa distância geográfica separando os exemplares amostrados no sistema baixo rio Paraná em comparação àqueles do alto rio Paraná, os dados obtidos demonstraram P. nasus como único táxon válido. Dessa forma, diferentemente de outras espécies de Parodontidae que demonstraram diversificação quando comparados grupos pares residentes no baixo e alto rio Paraná, P. nasus demonstrou estruturação populacional e homogeneidade cariotípica.

ABSTRACT The ichthyofauna of the La Plata hydrographic basin is divided into Upper and Lower Paraná River systems due to the geographic isolation of the Sete Quedas waterfalls, currently flooded by the lake of the Itaipu dam. In Parodontidae, pairs of species, or groups of cryptic species were described between these systems. Although genetic isolation and speciation have already been proposed in other species in the group, Parodon nasus has been maintained as a valid species and distributed throughout the La Plata river basin. In this perspective, specimens of P. nasus from four different sampling sites in the Upper and Lower Paraná River systems were compared regarding the karyotypes, molecular analyzes of population biology and species delimitation to investigate their genetic and population isolation in the La Plata river basin. Despite a geographic barrier and the immense geographic distance separating the specimens sampled from the Lower Paraná River system compared to those from the Upper Paraná River, the data obtained showed P. nasus as a unique taxon. Thus, unlike other species of Parodontidae that showed diversification when comparing the groups residing in the Lower versus Upper Paraná River, P. nasus showed a population structure and a karyotypic homogeneity.

Abstract Boana comprises a diverse genus of Neotropical treefrogs, currently rearranged into seven taxonomic species groups. Although cytogenetic studies have demonstrated diversity in its representatives, the chromosomal mapping of repetitive DNA sequences is still scarce. In this study, Boana albopunctata, Boana faber, and Boana prasina were subjected to in situ localization of different repetitive DNA units to evaluate trends of chromosomal evolution in this genus. Boana faber and B. prasina had 2n=24 chromosomes, while B. albopunctata has 2n=22 and an intra-individual variation related to the presence/absence of one B chromosome. The location of 45S rDNA sites was different in the analyzed karyotypes, corroborating with what was found in the distinct phylogenetic groups of Boana. We presented the first description of 5S rDNA in a Boana species, which showed markings resulting from transposition/translocation mechanisms. In situ localization of microsatellite loci proved to be a helpful marker for karyotype comparison in Boana, commonly with cis accumulation in the heterochromatin. On the other hand, genomic dispersion of microsatellites may be associated with hitchhiking effects during the spreading of transposable elements. The obtained results corroborated the independent diversification of these lineages of species from three distinct phylogenetic groups of Boana.