Resumo Isbrueckerichthys é um gênero de cascudinhos (Siluriformes: Loricariidae) que reúne cinco espécies morfológicas nas terras baixas da bacia do Ribeira de Iguape e nas terras altas da bacia do rio Tibagi. Apesar da validação das espécies morfológicas, estudos moleculares não tinham sido realizados para investigar o fluxo gênico e delimitação molecular das espécies. Para tanto, comparamos sequências da região COI associadas à identificação molecular por código de barras visando uma análise de delimitação de espécies e dados populacionais entre I. alipionis, I. epakmos, I. duseni, I. cf. duseni, I. saxicola e I. calvus. Os dados de distância genética K2P, a análise de delimitação molecular de espécies e ramos bem sustentados na árvore filogenética validam I. alipionis, I. epakmos e I. duseni, e sugere I. cf. duseni como unidade taxonômica operacional molecular. Ainda, não foram observadas diferenças entre I. saxicola e I. calvus. A discordância entre espécies moleculares e morfológicas pode ser devida à recente dispersão e diversificação de alguns representantes de Isbrueckerichthys na fronteira das bacias de Ribeira de Iguape e Tibagi. Características de isolamento da região serrana da bacia do Ribeira de Iguape e eventos de capturas de cabeceiras para terras altas foram utilizadas para explicar a dispersão e os casos de especiação incipiente em algumas linhagens de Isbrueckerichthys. Siluriformes (Siluriformes Loricariidae Tibagi tanto I alipionis cf calvus K2P KP K P Ainda

Abstract Isbrueckerichthys is a genus of armored catfish (Siluriformes: Loricariidae) with five species in the lowlands from the Ribeira de Iguape basin and in the uplands of the Tibagi River basin. Despite the validation of the morphological species, molecular data to investigate gene flow and species delimitation have not been completed for all species. For this purpose, we compared sequences of COI region associated with barcoding molecular identification, aiming for a species delimitation analysis and generating population data of I. alipionis, I. epakmos, I. duseni, I. cf. duseni, I. saxicola, and I. calvus. The K2P genetic distance, molecular species delimitation analysis, and well-sustained branches in the phylogenetic tree validate I. alipionis, I. epakmos, and I. duseni, and suggest I. cf. duseni as a valid molecular operational taxonomic unit. However, no differences were detected between I. saxicola and I. calvus. The discordance between molecular and morphological species may be due to the recent dispersal of some Isbrueckerichthys representatives at the border between the Ribeira de Iguape and Tibagi basins. The isolation features of the mountainous region of Ribeira de Iguape basin and headwaters captures to uplands are presented to explain the dispersion and the cases of incipient speciation in Isbrueckerichthys lineages. Siluriformes (Siluriformes Loricariidae purpose identification I alipionis epakmos cf calvus KP K P distance wellsustained well sustained unit However basins lineages

Allozyme electrophoresis was used to examine 12 enzymatic systems in two populations of the genus Neoplecostomus from the Paraná River basin. Samples of Neoplecostomus sp. 1 were collected in Paraitinguinha stream of the Tietê River basin, in the municipality of Salesópolis, São Paulo State, and those of Neoplecostomus sp. 2 from São Domingos stream of the Rio Grande River basin, in the municipality of Muzambinho, Minas Gerais State. The genetic variability of the two populations was estimated by Nei's expected heterozygosity and was considered lower than average for populations of freshwater fish. The proportion of polymorphic loci was low (only 5.26% for the locus Idh). The low frequency of heterozygosity for both populations revealed a high fixation of alleles for each locus. Homozygote excess was observed in both populations. The values of Nei's genetic identity and the presence of loci with different allele frequencies in both populations may imply that the two populations belong to different species. The genetic variability between populations was compared to other data for loricariids.