The current analysis investigates whether the uplift of the Serra da Esperança and the Ponta Grossa Arch in the Serra Geral resulted in ichthyofaunistic changes in adjacent basins. For this, we describe the phylogeographic structure among populations of Trichomycterus collected in hydrographic basins in southern Brazil by using partial nucleotide sequences of the mitochondrial gene Cytochrome C Oxidase subunit I. Analyses revealed that the nomenclature Trichomycterus davisi fails to contain the whole genetic diversity range found in the collected specimens and indicates at least six genetic lineages in Trichomycterus. Diagnostic morphological characteristics not associated to T. davisi could be identified in some specimens from the Iguaçu Piquiri haplogroup, indicating the occurrence of species Trichomycterus stawiarski. The lack of morphological differences among the other clades clearly suggests a cryptic species case. Molecular analyses revealed at least five new species besides T. davisi in the hydrographic basins and support the interpretation that genetic structure in T. davisi species complex is explained by tectonic events intrinsic to the areas of influence of Serra da Esperança and the Ponta Grossa Arch which occurred around 1.7 My.
The preservation of natural environments guarantees the conservation of biodiversity and ecosystem processes. Biomonitoring programs in preserved sites can be carried out using molecular biomarkers, which reflect possible stresses that exist in the monitored location. The metallothionein (MT) proteins and isoenzyme Cytochrome P4501A (CYP4501A) are among the most used biomarkers and reflect the detoxification of metal and organic xenobiotics, respectively. This study aimed to assess the performance of these biomarkers in natural aquatic environments using a meta-analytic approach. The data search was conducted in ISI Web of Science™, considering papers published until August 2016. Studies included in this research needed to compare reference or control sites and sites under stress and be conducted in situ. In general, both biomarkers were useful when comparing control sites with sites under stress. Moreover, when the data were categorized into groups of organisms, mainly bivalves and fishes, there were differences between the groups and between the monitored environments, marine or freshwater. The use of these biomarkers in fish is suitable for freshwater environments, and bivalves are suitable for marine environments. We concluded that the concomitant use of vertebrate and invertebrate bioindicators is useful to develop an effective biomonitoring program and to avoid biases due the physiology of the selected bioindicator.
Hybridization seems frequent among Cichla species (peacock bass), as studies have reported hybrids in populations within and outside their natural range (the Amazon and Orinoco river basins). Cichla kelberi and C. monoculus were introduced to the São João river (Southeast Brazil) more than 20 years ago, where they successfully colonized different environments. In this system, specimens have coloration and morphology that differ from patterns observed in their native range, indicating that the contact between C. monoculus and C. kelberi eliminated reproductive isolation, leading to introgressive hybridization. In this context, we used the LWS and dlx2 genes and the random amplified polymorphic DNA technique to characterize Cichla species in the São João river and to detect possible hybridization processes. The genetic markers identified here showed mismatches between mitochondrial and nuclear DNA in C. monoculus and C. kelberi, sampled both in the reservoir and in the estuarine stretch. Fragments of nuclear DNA from both species, as well as the presence of mitochondrial DNA from one species associated with the nuclear genome of the other, provide strong evidence of hybridization associated with bidirectional genetic introgression. Because hybrids may be more resistant, competitive, and aggressive than their parental species, these invaders may pose a significant threat to native biodiversity in this and other coastal rivers of the region.
The genetic relationships of native or introduced Plagioscion squamosissimus in five Brazilian Neotropical basins were evaluated using the mitochondrial atpase6/8 genes. Results revealed that the population of the Tocantins River basin is more basal than the native populations of the Amazon and Parnaíba River basins. Moreover, the populations of P. squamosissimus that were introduced in the São Francisco and upper Paraná River basins originated from the population of the Parnaíba River.
The distribution of Phalloceros species is generally allopatric and restricted; however, Phalloceros harpagos has a wide distribution and exhibits morphological variation among populations from different Brazilian river basins. Different species delimitation tests using cytochrome C oxidase subunit I gene sequences indicated that P. harpagos is a species complex that comprises between 7 and 9 phylogroups. The separation of the Paraná and Paraíba do Sul River basins most likely caused the diversification of these phylogroups in the Miocene period. The majority of phylogroups have a narrow distribution; however, one phylogroup has a broad distribution, being found primarily in the Paraná, Ribeira de Iguape, and Iguaçu River basins. This distribution can be attributed to possible headwater capture events caused by the reactivation of faults and erosion in the quaternary. Estimates about the times of divergence based on molecular data could be used to infer the biogeographic processes related to the diversification of South American freshwater fish.
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