RESUMEN Las especies de anfibios de la familia Centrolenidae están adaptadas a vivir en regiones de elevada altitud, por lo que no sorprende que su mayor diversidad ocurra en la Cordillera de los Andes. Aquí expandimos el ámbito de distribución de Vitreorana ritae por más de 550 km al sur del río Amazonas. La identificación de la especie se realizó con base en la comparación de las características morfológicas, acústicas y moleculares (marcador mitocondrial 16S rRNA). Nuestro registro es el primero de este género para el Estado de Mato Grosso, Brasil, así como para la zona de transición entre los biomas Amazonía y Cerrado. Este registro es concordante con la hipótesis de que el bajo número de especies registradas en la planicie amazónica puede ser el resultado de un menor esfuerzo de muestreo. Observamos que, a pesar de la amplia distribución de la especie en la Amazonía, la mayoría de las características morfológicas diagnósticas de V. ritae se conservan. Sugerimos que los grandes ríos de la cuenca amazónica parecen no actuar como barrera geográfica para esta especie. Sin embargo, y como resultado de nuestro pequeño tamaño de muestra, se requerirán estudios acústicos y moleculares adicionales para confirmar esta hipótesis.

ABSTRACT Frogs of the family Centrolenidae are adapted to live at high altitudes, and so it is not surprising that their greatest diversity is in the Andes mountain range. Here we extend the known geographic distribution of Vitreorana ritae by more than 550 km towards southern Amazonia. The species was identified by morphological, acoustic and molecular characteristics (mitochondrial marker 16S rRNA). The records reported here are the first for the genus Vitreorana in the state of Mato Grosso, Brazil, as well as for the transition zone between the Amazonia and Cerrado biomes. These records are consistent with the hypothesis that the low number of species of centrolenids reported in the lowlands of the Amazon region may be the result of limited sampling. Even though V. ritae is distributed throughout the Amazon, most of its diagnostic morphological characteristics are conserved. Thus, the great rivers of the Amazon Basin do not seem to act as geographical barriers for this species; however, due to the limited sample size, further acoustic and molecular studies are needed to confirm this hypothesis.

Abstract Cytogenetic data can be useful for taxonomic and phylogenetic studies, as well as to provide information about chromosome evolution. Therefore, it may help design conservation priorities for some threatened species, such as anurans. Herein, we describe the karyotypes of Scinax constrictus and Ololygon centralis, native endemic species from the Brazilian Cerrado. Chromosome preparations for both species were stained with Giemsa for morphological analyses and then impregnated by the Ag-NOR method for localization of the nucleolar organizer region (NOR). Both species had 24 chromosomes, as confirmed by meiotic analyses, which showed 12 bivalents. Chromosome morphologies presented the same pattern for Scinax and Ololygon compared to species already karyotyped in both genera. The NOR was interstitially located in the long arm of pair 7 in S. constrictus, whereas in O. centralis it was found near the centromere in the long arm of pair 1, thus diverging from what is commonly found for other Ololygon species. Therefore, we provide the first description of the karyotype of O. centralis and the first report of the localization of the NOR for the karyotype of both species. Our study increases the cytogenetic knowledge in species of the genera Scinax and Ololygon, and provide support for further studies on the taxonomy, ecology, and evolution of hylid anurans.