Abstract
Cytogenetics can be a useful tool to assist in taxonomic problems by adding information to the widely used morphological and molecular approaches. These taxonomic problems are especially common in anurans, once they are very diverse, highly polymorphic, and present many cryptic species. The genus Thoropa Cope, 1865 is composed of six specialist species that reproduce in rocky outcrops and are distributed throughout the Atlantic Forest and Cerrado ecotones. Phylogenetic studies point to possible cryptic species within the T. miliaris group. To assist in the evolutionary and taxonomic understanding of this group, classical cytogenetic techniques were used to find possible molecular markers for the genus through rDNA5S, rDNA18S, and U2snDNA probes and analyze their chromosome distribution in the group of T. miliaris. Despite the well conserved karyotype under conventional staining and classical techniques, such as Ag-NOR, our C-banding results showed differences in the centromeric heterochromatin concentration between two populations of T. miliaris. Furthermore, some differences among the populations and species were found for rDNA5S and U2snDNA. This study contributes to a better understanding of the evolutionary relationships within the genus; however, the use of different probe sequences, such as satDNA, is essential for a more robust cytogenetic analysis.