Psammocambeva, a subgenus of Trichomycterus s.s., includes a clade endemic to south-eastern Brazil, the Psammocambeva alpha-clade (PAC), containing species with similar colour pattern and fin morphology, making difficult their identification without accurate examination. The greatest diversity of PAC species occurs in the Rio Paraíba do Sul basin area (RPSA), situated within the Atlantic Forest, one of the most important and endangered biodiversity centres in the world. Herein, we: perform a multigene phylogeny focusing on species of PAC; revise morphological characters diagnosing species of PAC from the RPSA, with special attention to those equivocally synonymised in a recent study; describe two new species, and provide a key for species identification. Molecular and morphological evidence supported the recognition of eight valid species belonging to four species complexes. Data indicated that T. auroguttatus, T. travassosi, and T. longibarbatus are valid species. Finally, we discuss the negative impacts of underestimating species diversity in regions under the intense process of natural habitat loss, concluding that integrative approaches are important tools to estimate species diversity, but they should include a range of morphological characters informative to delineate and diagnose groups and their respective species, in association with phylogenies generated by robust molecular datasets.

The Rio Doce basin is situated in a biodiversity hotspot, with some fish groups still superficially known. The intense process of habitat loss and water contamination justifies efforts to speed up the pace of describing fish species diversity. Herein, we focus on a clade of trichomycterine catfishes, subgenus Psammocambeva, genus Trichomycterus, performing a multigene phylogenetic analysis, which integrated to a comparative morphological analysis corroborates monophyly and relationships of four species complexes. Five new species are recognised and described. Species distribution patterns support the recognition of five areas of endemism for trichomycterines, most of which are well-known biodiversity centres: Serra do Espinhaço, Serra do Brigadeiro, Serra do Caparaó, Serra do Castelo, and upper-middle Rio Doce. Trichomycterine diversity in the Rio Doce basin, with 16 species, of which 15 belong to Psammocambeva, is lower than in the smaller neighbouring Rio Paraíba do Sul basin, with 21 species in five subgenera. Data suggest that species diversification in the former basin is relatively younger, following the initial diversification of Psammocambeva in the Miocene, whereas diversification in the latter basin has been estimated to have occurred during the Oligocene. This study reinforces the importance of naming new taxa and delimitating areas of endemism as primary tools for conservation strategies.

The Cambeva variegata group (CVG) is endemic to a region situated in the intersection of two endangered biodiversity hotspots, Cerrado and Atlantic Forest, and drained by two important South American river basins, the upper Rio Paraná and upper Rio São Francisco basins. Presently, CVG comprises two nominal species, besides some still undescribed. We first performed a molecular phylogenetic analysis (total of 3368 bp) for five species of the CVG and 30 outgroups, which supported the monophyly of the CVG and its inclusion in Cambeva. Most morphological character states distinguishing the CVG from congeners are also present in Scleronema, possibly consisting of plesiomorphic features. We also performed the first time-calibrated phylogeny of the group, which supported possible relationships between present geographical distribution patterns and palaeogeographical events. The estimated time of origin of CVG in the Middle Miocene is nearly contemporaneous to a past hydrographical configuration when part of the upper Rio Paraná basin was connected to the Rio São Francisco basin. The first CVG lineage split occurring in the Miocene end corresponds to a major break in that palaeo basin. Species diversification between the Pliocene and early Pleistocene is compatible with final drainage rearrangement. This study highlights the urgent need for more detailed studies on the diversity and phylogenetic relationships of still poorly known organisms in this highly diverse and threatened region.

Trichomycterinae catfishes often have high intraspecific variability in colour patterns that may be associated with ontogenetic changes or habitat preferences. In species of the eastern South American genus Trichomycterus s.s., some cases of chromatic polymorphism have been reported but colour pattern is still considered an important tool for species identification. Herein, we first describe chromatic polymorphism in the geographically widespread T. jacupiranga, comparing populations from Tijuca National Park and Ribeira do Iguape basin, identifying four syntopic colour morphs. In addition, we performed a phylogenetic analysis using partial sequences of the mitochondrial gene 12Ss gene for 16 individuals of T. jacupiranga, with a maximum of 0.2% of genetic distance, corroborating T. jacupiranga as a single widespread species. Finally, based on our results and field observations, we concluded that it is not possible at the present to associate chromatic polymorphism in T. jacupiranga with habitat preferences, since specimens with different colouration in variable ontogenetic stages were found at the same microhabitats.