Comparative Cytogenetics and Molecular Phylogeography in the Group <i>Astyanax altiparanae – Astyanax </i>aff. <i>bimaculatus</i> (Teleostei, Characidae)

Abstract

The genus Astyanax comprises small characin fish of the neotropical region. The so-called ‘yellow-tailed characins’ compose one of the most widely distributed Astyanax groups. A. altiparanae and A. aff. bimaculatus, are evolutionarily closely related and commonly found in several Brazilian hydrographic basins. In the present work, chromosomal data of specimens of A. altiparanae and A. aff. bimaculatus from 4 hydrographic basins in the states of São Paulo (Upper Tietê, Paranapanema, Ribeira de Iguape) and Rio de Janeiro (Guapimirim) are shown. All the populations showed 50 chromosomes, with different karyotypic formula. Although only a single Ag-NOR bearing chromosome pair was observed, all populations possess multiple cistrons of 18S rDNA. FISH with the 5S rDNA probe showed single signals at the interstitial position of one metacentric chromosome pair. C-bands are distributed in the terminal and interstitial regions of several chromosomes. However, the As-51 satDNA are frugally located in a few chromosomes of fishes from Upper Tietê, Paranapanema and Guapimirim Rivers, being absent in individuals of A. aff. bimaculatus from Ribeira de Iguape River basin. Beside these 4 populations, molecular phylogeography studies were also performed in individuals from Middle and Lower Tietê River basin and from 2 additional collection sites in the Paranapanema and Ribeira de Iguape River basins. The phylogeographic analysis using 2 mtDNA regions (totalizing 1.314 bp of ND2 and ATPase6/8 genes) of 8 populations of the group of ‘yellow-tailed characins’ from 3 major hydrographic basins showed structuring of populations, suggesting a correlation between chromosomal (nuclear) and molecular (mitochondrial) data.

Molecular taxonomy and evolutionary hypothesis concerning Astyanax fasciatus (Characiformes, Characidae) from Vila Velha State Park and Tibagi and Iguaçu Rivers

“…Kavalco et al (2011) found monophyly in the A. altiparanae group, in agreement with the nominal redefinition proposed by Garutti and Britski (2000) for this species. However, when these authors analyzed the ND2 region of mtDNA, they found a possible paraphyly in the species that was attributable to sharing of haplotype groups between the Tietê and Paranapanema Basins.…”

“…The clustering between Astyanax sp (Iguaçu River) and A. fasciatus (Tibagi River) obtained in this study provides additional support for this hypothesis. According to Funk and Omland (2003), cryptic and taxonomically controversial species might interfere in the resolution of evolutionary trees; however, a polyphyletic condition might represent the real tree for the selected mitochondrial gene, and it might not be a simple artifact, depending on the branch-supporting values found in the tree (Kavalco et al, 2011).…”

“…In this context, molecular markers have been currently used as tools for assessing genetic variability and endemism, as well as phylogenetic and biogeographic relationships, in Astyanax altiparanae, A. schubarti, A. fasciatus, A. lacustris, and A. scabripinnis paranae (Prioli et al, 2002;Moysés and Almeida-Toledo, 2002;Leuzzi et al, 2004;Kavalco et al, 2011).…”

Karyotypic diversity among three species of the genus Astyanax (Characiformes: Characidae)

“…As occur with C-bands, the genus Astyanax also shows distinct patterns in relation to NORs, with single and multiple systems and with both intra-and inter-specific variations in number and locations on the chromosomes (Kavalco and Moreira-Filho, 2003;Pazza et al, 2006;Capistano et al, 2008;Kavalco et al, 2011). In this study a multiple marking system was only found in Astyanax aff.…”

“…bimaculatus showed the same diploid number (2n=50) but with differences in the karyotype formulas, probably due to rearrangements such as pericentric inversions. This last group, unlike the "scabripinnis group", has shown a constancy in the diploid number (Domingues et al, 2007;Pamponet et al, 2008;Ferreira Neto et al, 2009;Kavalco et al, 2011;Pacheco et al, 2011;Peres et al, 2011;Martinez et al, 2012), indicating an evolutionary karyotype pattern relatively more conserved than that of the "scabripinnis complex". In turn, the distinct karyotypes presented by the two populations of A. asuncionensis also show the occurrence of two karyomorphs and a probable "asuncionensis complex."…”