Oliveira A V, Prioli A J, Prioli S M A P, Pavanelli C S, Júlio H F, Panarari R S
Research Nucleus in Limnology, Ichthyology and Aquaculture, State University of Maringá, PR, Brazil.
Genetica. 2002 Aug;115(3):259-67. doi: 10.1023/a:1020633710622.
Whereas four species of the genus Steindachnerina occur in the Paraná river basin, S. insculpta was the only endemic species of the region under analysis, which is the third lower section of the upper Paraná river. Among other factors, this species has been characterised by the absence of spots in the basal region of the dorsal fin. However, various specimens with this characteristic appeared in the region after the construction of the Itaipu Hydroelectric Plant in 1982. An analysis of the genetic variability of Steindachnerina populations with or without spots is provided. Specimens were collected in different sites of the floodplain of the upper Paraná river and samples were compared by random amplified polymorphic DNA (RAPD) technique and morphological analyses. Ninety-eight amplified loci with nine random primers were analysed in 19 specimens of each phenotype. Data for genetic distance showed great divergences between the two phenotypes and indicate two different species. Spotted specimens may be identified as S. brevipinna, found in the region downstream Sete Quedas Falls. The species must have overcome the geographical barrier during the building of the Itaipu hydroelectric dam that submerged the waterfalls and which became an obstacle between the upper and middle Paraná river some 150 km downstream. Since phenotypes do not share dominant alleles, absence of gene flow has been suggested.
虽然斯坦达奇纳丽鱼属的四个物种出现在巴拉那河流域，但雕刻斯坦达奇纳丽鱼是所分析区域（即巴拉那河上游的第三下游段）的唯一特有物种。在其他因素中，该物种的特征之一是背鳍基部区域没有斑点。然而，1982年伊泰普水电站建成后，该区域出现了各种具有这一特征的标本。本文对有斑点和无斑点的斯坦达奇纳丽鱼种群的遗传变异性进行了分析。在上巴拉那河漫滩的不同地点采集标本，并通过随机扩增多态性DNA（RAPD）技术和形态学分析对样本进行比较。对每种表型的19个标本用9种随机引物分析了98个扩增位点。遗传距离数据显示这两种表型之间存在很大差异，表明是两个不同的物种。有斑点的标本可能被鉴定为短鳍斯坦达奇纳丽鱼，在塞特克达斯瀑布下游区域发现。该物种一定是在伊泰普水电站建设期间越过了地理障碍，当时该水电站淹没了瀑布，而瀑布在下游约150公里处成为了巴拉那河上游和中游之间的障碍。由于两种表型不共享显性等位基因，因此有人提出不存在基因流动。
