Fine-scale genetic structure patterns in two freshwater fish species, Geophagus brasiliensis (Osteichthyes, Cichlidae) and Astyanax altiparanae (Osteichthyes, Characidae) throughout a Neotropical stream.

Streams are very important environments for Neotropical freshwater fish fauna, and possess a high number of species. These small drainages are also highlighted by their intrinsic biological and physicochemical features; however, knowledge on the genetic distribution of fish in these drainages is limited. Therefore, in the present study, RAPD (random amplified polymorphic DNA) and microsatellite markers were used to analyze population differentiation and gene flow of Astyanax altiparanae and Geophagus brasiliensis from three sites (high, medium, and low) throughout the Penacho stream (about 32 km long), which is a Neotropical stream. Both markers revealed higher levels of genetic diversity levels for A. altiparanae (: 90.05; HS: 0.350) compared to G. brasiliensis (: 30.43; HS: 0.118), which may be related to the particular biology of each species. AMOVA revealed significant genetic variation among populations of each species. All pairwise ΦST values were significant, ranging from 0.020 to 0.056 for A. altiparanae samples, and from 0.065 to 0.190 for G. brasiliensis samples. Bayesian clustering analysis corroborated these results and revealed clusters of both A. altiparanae (two based on RAPD data) and G. brasiliensis (two based on RAPD data and three on microsatellite data). Gene flow estimates showed that there were similar rates of migration among A. altiparanae samples and low rates of migration among some G. brasiliensis samples. These results suggest patterns of fine-scale genetic structure for both species in the Penacho stream. This information may enhance knowledge of Neotropical streams and may be useful for future management and conservation activities.

Isolation and characterization of 13 polymorphic microsatellite loci in Hypostomus ancistroides (Teleostei, Loricariidae) and cross-amplification in related species.

This study details 13 novel polymorphic microsatellite loci in the armoured catfish Hypostomus ancistroides, and assesses their utility for population genetic studies. The analysis of 30 individuals revealed a total of 99 different alleles (ranging from two to 15 alleles per locus), with an average of 7·62 alleles per locus, with observed and expected heterozygosities ranging from 0·103 to 0·931 and from 0·102 to 0·906, respectively. One of the 13 loci showed significant deviations from Hardy-Weinberg equilibrium, probably due to the presence of null alleles, inferred from the excess of homozygotes.

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

Most studies of diversity and genetic structure in neotropical fish have focused on commercial species from large rivers or their reservoirs. However, smaller tributaries have been identified as an important alternative migratory route, with independent pools of genetic diversity. In this context, the present study aimed to evaluate genetic diversity and structure in five neotropical fish species from a region of Laranjinha River in the upper Paraná River basin. PCR-RAPD (random amplified polymorphic DNA) markers were used to characterize around 40 individuals of each species distributed upstream and downstream of Corredeira Dam that interrupts the river. The descriptive index of genetic diversity (P = 30.5-82%; HE 0.122-0.312) showed that the populations have acceptable levels of genetic diversity. The values for Nei's genetic distance (DN min 0.0110 and max 0.0306) as well as the genetic structure index and the analysis of molecular variance (AMOVA, ϕST min 0.0132 and max 0.0385) demonstrated low, but significant levels of genetic structure. Bayesian analysis of assignment found two k clusters, including several individuals with mixed ancestry for all populations from the five species analyzed. These findings along with historical data on rainfall and the low dimensions of the dam studied here support the hypothesis that periodic floods enable the transit of individuals between different localities mitigating the differentiation process between populations.

Development and characterization of 14 microsatellite loci in the Neotropical fish Geophagus brasiliensis (Perciformes, Cichlidae).

Fourteen polymorphic microsatellite loci were isolated and characterized for the Neotropical cichlid Geophagus brasiliensis and tested on 30 individuals belonging to a single population. Among the 14 loci described, four showed potential presence of null alleles, inferred from the excess of homozygous genotypes, and three of these loci showed significant deviations from Hardy-Weinberg equilibrium. Fifty-nine different alleles were detected (ranging from two to eight alleles per locus), with estimates of observed and expected heterozygosity ranging from 0·167 to 0·700 and from 0·269 to 0·825. Cross-amplification of primers was successful in five other cichlid species.