Diferenciação genética e relações filogenéticas entre as linhagens de Microsternarchus (Gymnotiformes: Hypopomidae) na bacia do rio Negro, em função de marcadores moleculares mitocondriais e nucleares

AUTOR(ES)
FONTE

IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia

DATA DE PUBLICAÇÃO

17/06/2011

RESUMO

The neotropical electric fish (Order Gymnotiformes) possesses, as one of their main characteristics, the ability to generate and detect alternating electric currents by the action of an electric organ end electroreceptors, respectively. The Electrogenic and Eletrosensory System (EES), allows these fishes to exploit the environment in which they live and to communicate, becoming a fundamental element for the inter- and intra-specific differentiation as well as for reproductive isolation and speciation processes. Studies about the basic biology of this group are scarce, and several taxonomic problems within the order exist, as in the monotypic genus Microsternarchus, which has only one species described, M. bilineatus. Previous studies identified subtle variations in the external morphology, in the characteristics of the Electric Organ Discharge - EOD (a species-specific character) and also in the nucleotide sequences of the mitochondrial DNA control region, the mitochondrial gene COI and the exon III of the nuclear gene RAG-1, suggesting that Microsternarchus, despite being considered as a monotypic genus, may contain species not yet described. Aiming to address the genetic diversity of this genus and thus identify putative distinct lineages within Microsternarchus through the DNA barcode technique, 365 sequences of COI were obtained from individuals collected along 46 tributaries in the Negro river, nine in the Branco river, one in the Tapajós river and one in the Amazon river. From the lineages identified by the COI gene, sequences of the control region of 20 individuals of each lineage were obtained as well as sequences of the RAG-1 gene of approximately 10 individuals of each lineage. The sequence analysis of the COI gene allowed the identification of five lineages (A, B, C, D and E), with the lineages C, D and E showing greater diversity, i. e., they showed the highest values of genetic divergence among its individuals, allowing the identification of sub-lineages within each one of them. All three markers (COI, D-Loop and RAG-1) were effective in recovering the lineages A, B, C+D and E as monophyletic groups in all the analysis and with high bootstrap values, however the relationship between these lineages was not congruent between the different markers. In addition, for the three markers, high values of genetic divergence between lineages A, B, C+D and E were also obtained, but the lowest value was found among the lineages C and D, reflecting the fact that they were not recovered as monophyletic groups in all the analyses. The high divergence values, the monophyly of the lineages A, B, C+D and E, as well as the existence of variations in external morphology and characteristics of the EOD (in the case of lineage A), suggest that these lineages are evolving separately and thus can be considered new species. This work, thus, points to the need of a taxonomic revision in the genus Microsternarchus.

ASSUNTO(S)

genetica animal microsternarchus marcadores moleculares peixe elétrico dna barcoding

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