A multi-approach analysis of the genetic diversity in populations of Astyanax aff. bimaculatus Linnaeus, 1758 (Teleostei: Characidae) from Northeastern Brazil

Abstract

Few reports are available about the ichthyofauna of typical semi-arid rivers, although the regional diversity has been constantly threatened by human activities, mainly related to impoundment and construction of dams. The goal of the present work was to evaluate using different methods, the population genetic structure of a characin fish, Astyanax aff. bimaculatus, widespread throughout hydrographic basins of Bahia, Northeastern Brazil. Morphological (meristic and morphometric data), cytogenetic (karyotype and Ag-NOR), and molecular (RAPD and SPAR) analyses were carried out in specimens collected upstream and downstream of Pedra Dam, in the main channel of Contas River (Contas River Basin), and in the Mineiro stream, which belongs to the adjacent Recôncavo Sul basin. Few external differences were detected among populations, where the individuals collected upstream of Pedra Dam were slightly larger than the others. Cytogenetic data also showed a similar karyotypic pattern (2n=50; 6m+28sm+12st+4a; FN= 96) and NORs located on the short arms of up to two chromosome pairs, with numerical inter- and intra-populational variation. Nonetheless, RAPD and SPAR analyses differentiated reliably the three populations, revealing striking differences in the allele frequencies among the localities studied and a significant difference in population structure index (Fst=0.1868, P<0.0001). The differences between populations within a same river were as significant as those between distinct hydrographic basins, indicating that the dam/reservoir represents an effective barrier to gene flow. Additionally, environmental peculiarities from each locality are also believed to influence the genetic patterns detected herein. On the other hand, the similarity between samples from Contas River and Recôncavo Sul basins could be related to a common evolutionary history, since both basins are geographically close to each other. Finally, the present study shows that a multi-approach analysis is particularly useful in identifying the population structure of widely distributed species and to evaluate the impacts of human activities on natural fish populations.<br>Poucos estudos ictiofaunísticos estão disponíveis em rios típicos do semi-árido, apesar da constante ameaça à diversidade local devido a influências antrópicas, com destaque para o represamento e construção de barragens. O presente trabalho teve como objetivo avaliar, por meio de diferentes metodologias, a estrutura genética de populações de uma espécie de caracídeo, Astyanax aff. bimaculatus, amplamente distribuída em bacias hidrográficas da Bahia, Nordeste do Brasil. Análises morfológicas (dados merísticos e morfométricos), citogenéticas (cariótipo e Ag-RONs) e moleculares (RAPD e SPAR) foram realizadas em espécimes coletados à montante e à jusante da Barragem da Pedra, na calha principal do médio rio de Contas (bacia do Rio de Contas) e no ribeirão Mineiro, pertencente à bacia adjacente do Recôncavo Sul. Poucas diferenças externas foram detectadas entre as populações, sendo os indivíduos...

Genetic analysis of five sedentary fish species in middle Laranjinha River (upper Paraná River basin): A case study

“…The highestP and H E values were observed in A. altiparanae and the lowest values in L. amblyrhynchus (Table 2). All levels of genetic diversity in the populations studied here were evaluated as satisfactory compared to previously reported data (Chiari and Sodré, 2001;Almeida et al, 2003;Leuzzi et al, 2004;Pamponet et al, 2008). …”

“…Significant genetic structure differences were found between populations of Pimelodus maculatus fragmented by dams in Paranapanema (Almeida et al, 2003), suggesting that this fragmentation has increased the rate of differentiation, which was initially caused by the existence of several natural waterfalls. Pamponet et al (2008) also found significant genetic structure differences between populations of Astyanax aff. bimaculatus in southeast Bahia that were separated by dams.…”

“…Previous studies using RAPD reported the following values ofP: Schizodon intermedius 45.5%, Schizodon nasutus 41.4%, Leporinus amblyrhynchus 29.3%, Leporinus friderici 46.3%, Leporinus striatus 41%, Leporinus octofasciatus 55.1%, Leporinus elongatus 58.7%, and Leporinus obtusidens 53.1% (Chiari and Sodré, 2001); Astyanax altiparanae 78.41% (Leuzzi et al, 2004), Astyanax aff. bimaculatus 85.71% (Pamponet et al 2008), Pimelodus maculatus 50.1-60.94% (Almeida et al, 2003), and Steindachnerina insculpta 76.6% (Oliveira et al, 2002). By comparison, we foundP values of 82.0% to 30.5%, and H E levels of 0.312 to 0.122 in the five species studied here.…”

“…Several studies have shown variations in genetic structure in neotropical fish populations due to isolation by distance in non-migratory species (Leuzzi et al, 2004;Sofia et al, 2006;Pamponet et al, 2008) or by formation of demes influenced by biological factors in species with a migratory habit (Wasko and Galetti Jr., 2002;Hatanaka and Galetti Jr., 2003). In neotropical fish populations fragmented by dams, there is a tendency towards changes in genetic structure when gene flow is disrupted.…”

Performance of human immunostimulating agents in the improvement of fish cytogenetic preparations

“…This approach has been routinely tested on an array of fish species from several orders such as Perciformes (Sena and Molina, 2007), Anguilliformes (Vasconcelos and Molina, 2009), Beryciformes (Bacurau and Molina, 2004), and Characiformes (Medrado et al, 2008;Pamponet et al, 2008), among others.…”