Variabilidade genética, estrutura populacional e filogeografia do mapará (Hypophthalmus marginatus Valenciennes, 1840 - Pimelodidae, Siluriformes) no Estado do Pará, utilizando sequências de DNA mitocondrial
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2012-06-29Autor
http://lattes.cnpq.br/3441674902981435
FERREIRA, Edinaldo Silva
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The maparás Hypophthalmus spp. have contributed substantially to the fish landings
in the Amazon region, although the population-genetic aspects about their is poorly
known. Therefore, this study aims to evaluate the genetic variability, population
structure and phylogeography of the most commercialized species, H. marginatus, in
eight localities in the State of Pará, to provide information supporting sustainable
exploitation policies for the species. We obtained 547 bp of the control region of
mitochondrial DNA from 241 individuals of H. marginatus. The phylogenetic tree
separated the individuals into two monophyletic clades, called Type I and Type II,
with high bootstrap values, which suggests its division into two species. This was
supported by the high genetic divergence of 8.8% between the types, the network of
haplotypes where the haplogroups I and II were separated by 44 mutations, the
analysis of molecular variance whereas 83.77% of the variance was attributed to
differences between groups, and the fixation index values greater than 0.82
indicating absence of gene flow mediated by females between the two groups. The
two types of H. marginatus coexist in the Tapajós and Xingu, and only Type I occurs
in the Amazon, Tocantins and Pará River estuary, while only the Type II occurs in the
Anapú river. Therefore, studies involving larger samples and other rivers of the
Amazon should be performed to define the actual range of each type of H.
marginatus. Genetic diversity was high in all populations of Types I and II, suggesting
that fishing pressure does not reduce, in the short term, the genetic variability of the
species. The analysis of population within the Types I and II suggests the absence of
genetic substructuring associated to the tributaries assessed, rejecting the
hypothesis of philopatry for H. marginatus and indicating that the migratory ability of
these taxa or the flood regime of the Amazonian floodplains may be responsible for
the genetic similarity between most populations within groups. Furthermore, the
genetic differences observed between populations of the Type I may be the result of
random genetic drift or diachronic spawns. For Type I the negative and significant
test of neutrality of Fu (Fs) can be associated with the effect of background selection
or hitchhiking since population expansion should not be the cause of these results
because the indices of genetic diversity and mismatch distribution give evidence of
stable populations over evolutionary time. For Type II, the neutrality tests, the genetic
diversity and mismatch distribution suggests stable populations over time. Finally, for
purposes of management and conservation of Hypophthalmus the present work
indicates the presence of at least four species in the Pará state rivers and suggests
that studies expanding the collecting area and using nuclear markers are necessary
to know the actual diversity of this genus in Amazon.
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