High rDNA polymorphisms in Astyanax lacustris (Characiformes: Characidae): new insights about the cryptic diversity in A. bimaculatus species complex with emphasis on the Paraná River basin

Abstract This study aimed to identify species of Astyanax bimaculatus group from four Itaipu Reservoir tributaries (Paraná River Basin) by cytogenetics and molecular markers (COI) investigate the possible occurrence cryptic diversity in part this basin. The populations showed only one karyotype formula simple AgNORs. FISH with 18S rDNA probe a high variation, 5S probes evidenced sites most specimens, although multiple are present two specimens. variations cistrons generated 13 cytotypes. data did not reveal populations; however, its grouping 82 sequences other stretches Paraná Basin originated three haplogroups (distances 3.12% 8.82%) 33 haplotypes were identified. DNA Barcode suggests that cytogenetic represent polymorphism degree, it identified analyzed specimens as lacustris, which confirms morphological identification. Our suggest is different than proposed synonymizations A. altiparanae asuncionensis lacustris. reinforces importance integrative methods for taxonomy.