Invasion, dispersion and hybridization of fish associated to river transposition: karyotypic evidence in Astyanax “bimaculatus group” (Characiformes: Characidae)

Invasion, dispersion and hybridization of fish associated to river transposition: karyotypic... The Astyanax species of the bimaculatus group include morphologically similar representatives that share the same color pattern, corresponding to at least 20 species. Specimens from the São Francisco River basin and from the Grande River (Upper Paraná basin) are included in this group. In the early 1960’s, the Piumhi River, an original tributary of the Grande River, was transposed to the São Francisco River basin due to the construction of the Furnas Hydroelectric Power, in the state of Minas Gerais, Brazil. In this context, we characterized representatives of the bimaculatus group from both basins and from the transposition region of the Piumhi River, using chromosome characteristics obtained by conventional analyzes and fluorescence in situ hybridization with rDNA probes. All the analyzed specimens presented 2n = 50 chromosomes and similar localization of the nucleolus organizer regions (Ag-NORs), 18S rDNA and 5S rDNA sites. However, diagnostic chromosome differences were detected concerning the number of submetacentric and acrocentric chromosomes in the karyotypes, making possible the characterization of five distinct karyotypes (Cytotypes A–E), where the specimens from the São Francisco and from the Grande River correspond to Cytotypes A and B, respectively. In addition, these two Cytotypes were sympatrically found in the Piumhi River with specimens carrying a clear intermediate karyotype (Cytotype C), as well as with others harboring different karyotypes (Cytotypes D and E). Our data indicate that Cytotypes A and B probably diverged from each other during the prior geographic isolation. However, despite their chromosomal differentiations, they still maintain a close relationship which allows interbreeding and the formation of a secondary hybrid zone, due to the breakdown of the geographic isolation. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Reviews in Fish Biology and Fisheries Springer Journals

Invasion, dispersion and hybridization of fish associated to river transposition: karyotypic evidence in Astyanax “bimaculatus group” (Characiformes: Characidae)

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Publisher
Springer Netherlands
Copyright
Copyright © 2011 by Springer Science+Business Media B.V.
Subject
Life Sciences; Freshwater & Marine Ecology; Zoology
ISSN
0960-3166
eISSN
1573-5184
D.O.I.
10.1007/s11160-011-9246-2
Publisher site
See Article on Publisher Site

Abstract

The Astyanax species of the bimaculatus group include morphologically similar representatives that share the same color pattern, corresponding to at least 20 species. Specimens from the São Francisco River basin and from the Grande River (Upper Paraná basin) are included in this group. In the early 1960’s, the Piumhi River, an original tributary of the Grande River, was transposed to the São Francisco River basin due to the construction of the Furnas Hydroelectric Power, in the state of Minas Gerais, Brazil. In this context, we characterized representatives of the bimaculatus group from both basins and from the transposition region of the Piumhi River, using chromosome characteristics obtained by conventional analyzes and fluorescence in situ hybridization with rDNA probes. All the analyzed specimens presented 2n = 50 chromosomes and similar localization of the nucleolus organizer regions (Ag-NORs), 18S rDNA and 5S rDNA sites. However, diagnostic chromosome differences were detected concerning the number of submetacentric and acrocentric chromosomes in the karyotypes, making possible the characterization of five distinct karyotypes (Cytotypes A–E), where the specimens from the São Francisco and from the Grande River correspond to Cytotypes A and B, respectively. In addition, these two Cytotypes were sympatrically found in the Piumhi River with specimens carrying a clear intermediate karyotype (Cytotype C), as well as with others harboring different karyotypes (Cytotypes D and E). Our data indicate that Cytotypes A and B probably diverged from each other during the prior geographic isolation. However, despite their chromosomal differentiations, they still maintain a close relationship which allows interbreeding and the formation of a secondary hybrid zone, due to the breakdown of the geographic isolation.

Journal

Reviews in Fish Biology and FisheriesSpringer Journals

Published: Nov 18, 2011

References

  • Cytogenetic identification of invasive fish species following connections between hydrographic basins
    Bellafronte, E; Moreira-Filho, O; Vicari, MR; Artoni, RF; Bertollo, LAC; Margarido, VP
  • Characterization of invasive fish species in a river transposition region: evolutionary chromosome studies in the genus Hoplias (Characiformes, Erythrinidae)
    Blanco, DR; Lui, RL; Bertollo, LAC; Diniz, D; Moreira-Filho, O

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