No abstract

Over the past few decades, South American Rivers, including the Paraná River system, have been intensely impacted by dam constructions. To mitigate adverse impacts, fish passages were incorporated into two large dams on the Paraná River (Itaipu and Porto Primavera) to reestablish longitudinal connectivity, which is very important for conserving populations of migratory fish species. The aim of this study was to estimate genetic diversity, population differentiation and gene flow, using microsatellites markers and mitochondrial haplotypes (D-loop), in populations of Prochilodus lineatus, a long distance migratory species commonly found in Paraná River basin drainages. Samples were obtained from six locations in the Upper and Middle Paraná River: Porto Primavera Reservoir, downstream of the Porto Primavera Reservoir, four tributaries of this reservoir (Pardo, Peixe, Verde and Aguapeí Rivers) and in the Iguaçu River, downstream of the Itaipu dam. High genetic diversity was observed in all samples, as expected for species with large population sizes and high migration rates. However, the influence of other factors, such as secondary contacts, fish passages and restocking were also suggested. In general, evidence of spatial population structuring was not found, even though there were two large dams in the study area. This could also be attributed to the brief period that has elapsed since the dams were built, the influence of migratory and reproductive patterns and the possible contributory effects of the fish passages. Furthermore, the absence of population structuring also corroborates existing information that emphasizes the importance of unimpeded tributaries for conserving migratory fish populations in fragmented watersheds.

The focus of this work was to survey the ichthyofauna of the Penacho stream, a tributary of the Laranjinha River, northeastern Paraná State, in an area of the Upper Paraná River basin still devoid of ichthyofaunal studies. In general, the banks of the Penacho Stream are predominantly characterized by pasture or agricultural activities and may exhibit little riparian vegetation in few stretches. Fishes were collected at eight different locations, from its headwaters to its mouth, between February 2009 to March 2010. A total of seven orders, twelve families and thirty-three species, three of which not native to the basin, were reported. The fish species captured along the Penacho stream are those that still manage to stay in those environments, even in changed conditions. However, to better understand the effects of degradation on fish diversity, it is necessary to monitor it along time.

Gymnogeophagus setequedas is a rare and rheophilic species of tribe Geophagini, considered endangered in Brazilian red lists. Its previously known geographical distribution range was the Paraná River basin, in Paraguay, and a tributary of the Itaipu Reservoir in Brazil. Since its description no specimens have been collected in the original known distribution area. However, recent records of G. setequedas in the lower Iguaçu River, in a region considered highly endemic for the ichthyofauna, extended the known geographical distribution and may represent one of the last remnants of the species. The aim of this study was to estimate the genetic diversity and population structure of G. setequedas, using microsatellite markers and mitochondrial haplotypes, in order to test the hypothesis of low genetic diversity in this restricted population. Muscular tissue samples of 86 specimens were obtained from nine locations in the Lower Iguaçu River basin, between upstream of the Iguaçu Falls and downstream of the Salto Caxias Reservoir. Seven microsatellites loci were examined and a total of 120 different alleles were obtained. The number of alleles per locus (NA) was 17.429, effective alleles (NE) 6.644, expected heterozygosity (HE) 0.675, observed (HO) heterozygosity 0.592, and inbreeding coefficient (FIS) 0.128. Twelve haplotypes in the D-Loop region were revealed, with values of h (0.7642) and π (0.00729), suggesting a large and stable population with a long evolutionary history. Thus, both molecular markers revealed high levels of genetic diversity and indicated the occurrence of a single G. setequedas population distributed along a stretch of approximately 200 km. The pattern of mismatch distribution was multimodal, which is usually ascribed to populations in demographic equilibrium. Nevertheless, the construction of a new hydroelectric power plant, already underway between the Salto Caxias Reservoir and Iguaçu Falls, could fragment this population, causing loss of genetic diversity and population decline, and for this reason it is necessary to maintain the Iguaçu River tributaries and downstream area from the Lower Iguaçu Reservoir free of additional dams, to guarantee the survival of this species.

The Neotropical brown stink bug, Euschistus heros (Fabricius) (Hemiptera: Pentatomidae), is a major Brazilian soybean pest. Aiming to provide relevant information to implement pest and insecticide resistance management, new microsatellite loci were developed for E. heros and used in a study of genetic diversity and population structure. The population analysis was performed using eight microsatellite loci from 17 samples (n = 243 individuals) collected in the major soybean‐producing regions in Brazil (northeastern, midwestern, and southern regions). These microsatellite loci provided high genetic diversity values on the whole extension for the studied region (He = 0.895; total number of alleles = 400). Neotropical brown stink bug populations in general displayed low genetic structure levels among the samples (overall ΦST = 0.009). An exception was the sample from the northeastern region, which showed a significant genetic differentiation (pairwise ΦST = 0.031–0.063). Bayesian cluster analysis confirmed these results, did not show population subdivision, and indicated considerable levels of gene flow. Significant correlations between genetic differences and geographic distance were obtained. The lowest estimate of migration was found in the population from São Desidério, which was also the most distant from the remaining populations based on genetic distance. Some plausible hypotheses for the low genetic differentiation among these populations are the fast expansion of soybean production areas, the main food source of E. heros, polyvoltinism, and possible influence of anthropogenic dispersal. All these factors could have led to high population densities, a wide distribution that may contribute to reduced population differentiation, and increased genetic diversity.