Allozyme relationships in hypostomines (Teleostei: Loricariidae) from the Itaipu Reservoir, Upper Rio Paran� basin, Brazil

Abstract

In an allozyme electrophoresis survey of 15 hypostomine species from the Itaipu Hydroelectric Reservoir, 25 loci from 14 enzyme systems were scored. Allozyme data allowed recording diagnostic genetic markers for all species analyzed and for some species groups within Hypostomus, a taxon which is taxonomically still unresolved in the Upper Rio Paraná basin. The mean expected heterozygosity of the species was considerably variable and hypotheses to tentatively explain this variation are discussed. A cladogram based upon the allelic frequencies of the species analyzed was produced by the continuous maximum likelihood method: Rhinelepis aspera and M. parananus were separated from the species of Hypostominae by a long branch length. Pterygoplichthys anisitsi was the sister of all the representatives of the genus Hypostomus. Within Hypostomus, two main clades were produced: in the first, H. cochliodon was the sister of the species comprising the H. plecostomus group, and in the second, the tree showed the following relationships: (H. albopunctatus (H. regani + Hypostomus sp. 3) + (H. margaritifer (H. microstomus (Hypostomus sp. 1 (H. ternetzi + Hypostomus sp. 2)). Hypostomus ternetzi and Hypostomus sp. 2 are referred to here as representatives of the H. ternetzi group.

Genetic diversity of Hypostomus ancistroides (Teleostei, Loricariidae) from an urban stream

“…Actually, while low He values (from zero to 0.028) have been observed for populations of three species of Hypostomus , relatively higher levels of heterozygosity (He = 0.082 and 0.052) were reported for populations of H. ancistroides from Itaipu Reservoir and Corumbá River . The levels of He observed in all samples of H. ancistroides from Cambé stream were even higher (0.1022 to 0.1526) than those mentioned by Zawadzki et al (2005). However, this discepancy could be partially explained by the inherent differences between RAPD and allozyme techniques, since allozymes detect only about 1/3 of actual amino acid variation and do not detect synonymous changes, while RAPDs have the potential to detect practically all changes, independent of whether they cause amino acid changes or not.…”

Cytogenetic characterization of Hypostomus nigromaculatus (Siluriformes: Loricariidae)

“…Due to this large variation, molecular studies using allozymes and mtDNA have been carried out to help species identification and determine the phylogenetic relationships of some species within the genus (Zawadzki et al, 2001(Zawadzki et al, , 2005.…”

Allozyme variation among three populations of the armored catfish Hypostomus regani (Ihering, 1905) (Siluriformes, Loricariidae) from the Paraná and Paraguay river basins, Brazil

“…Similar findings were reported by Zawadzki et al (2002) for other Hypostomus species common to the Itaipu and Corumbá reservoirs. According to Zawadzki et al (2005) now in contact due to the formation of Itaipu Lake in 1982, which flooded and covered the falls at the mouth of each tributary which probably used to act as a geographic barrier to free gene flow. On the other hand, the Corumbá River is a tributary of the Paranaíba, a river with a relative degree of fish endemism (Pavanelli and Britski, 1999), which may promote endogamy which in turn causes low heterozygosity.…”