Integrating Genetic and Cytogenetic Data: A Diversity Study of and (Characidae) Species from the Paraná River Basin.

is one of the most specious fish groups in the Neotropical region, with many cryptic species, which represents a challenge for correct identification through traditional taxonomic methods. is a recently resurrected genus group of species previously belonging to , specifically those with extensive chromosomal variation of the and s complexes. In the present study, the mitochondrial genes cytochrome oxidase subunit 1 (COI), mitochondrial ATP synthase 6 and 8 (ATPase 6/8), and NADH dehydrogenase subunit 2 (ND2) were used in conjunction with chromosomal data to characterize molecularly and cytogenetically populations of and from rivers and streams of the Ivaí River Basin (Paraná Basin). The results demonstrated the effectiveness of the integrative use of molecular and cytogenetic techniques, with the confirmation of at least three species for the sampled sites: , , and , which showed inter- and intrapopulation karyotype variations. In addition, extensive haplotypic variation can be observed for these species within the Ivaí River Basin and throughout the Paraná River Basin. The data demonstrate a hidden diversity among the species analyzed, enrich the ichthyofaunistic knowledge of small rivers and streams, and contribute to future conservation projects in these areas.