Astyanax fishes are among the most important food-web components of South America rivers. In the Iguaçu River basin, the Astyanax genus is represented mainly by endemic species. For millions of years, that hydrographic basin has been geographically isolated from the Paraná River basin by the Iguaçu Falls. Recently, a species from the Upper Paraná River basin identified as Astyanax bimaculatus was revised and described as a new species named Astyanax altiparanae Garutti & Britski, 2000. Fauna endemism and geographic isolation triggered interest in investigations to evaluate the identification and genetic relatedness among two A. altiparanae populations from the Upper Paraná River basin and the population identified as A. bimaculatus in the Iguaçu River, upstream from the Iguaçu Falls. Mitochondrial DNA sequences and RAPD markers revealed high genetic diversity within each population, as well as low genetic distance, high gene flow, and high mitochondrial DNA similarity among all three populations. In conjunction with morphological similarities, these results demonstrated that the population presently known as Astyanax bimaculatus in the Iguaçu River should actually be stated as Astyanax altiparanae. Furthermore, it could be inferred that the A. altiparanae population is not endemic and most likely it was recently introduced in the Iguaçu River basin, maintaining the ancestral genetic identity.
Astyanax; fish; D-loop; control region; mitochondrial DNA; RAPD
