Avaliação da seqüência nucleotídica do gene mitocondrial citocromo oxidase I na identificação de espécies de peixes neotropicais.

Abstract

DNA barcoding was defined as a standard methodology for quantifying the global biodiversity through a mitochondrial gene portion cytochrome c oxidase I (COI). As decision making for species identification, a threshold of 10X between variation intra-specific and interespecific was stipulated. The neotropical fish community is considered the most diverse with high number of endemic species and cryptic taxa. In order to help minimizing the taxonomic impediment and identification of fish species of neotropical region, the criterion of DNA barcoding was evaluated regarding the effectiveness in distinguishing pairs of close species with consistent taxonomic description. Fragments of approximately 535 bp from 20 species assigned in seven genera were analyzed. The analyzes were conducted based on the Kimura-2-Parameter distance model and neighbor-joining algorithm. There were similarities between species congeneric haplotypes of Potamotrygon and Schizodon. The average genetic distances intra-specific and interespecific varied from 0 to 0.3% and 0.3 to 16.8%, respectively. Thirteen pairs of species obtained values of genetic diversity enough to be identified by the COI sequences. One pair of species of the genera Potamotrygon (P. falkneri e P. motoro), Pseudoplatystoma (P. reticulatum e P. punctifer), Salminus (S. brasiliensis e S. hilarii), Steindachnerina (S. brevipinna e S. insculpta) and three species of Schizodon (S. borellii, S. intermedius e S. fasciatus) not reached the threshold stipulated by the project, consequently were not differentiated by COI sequence. It is possible to conclude that the microgenomic identification system for fish of Neotropical region must be used with caution to avoid an underestimate the biodiversity and discrimination work of species involving information in various areas may help to minimize the taxonomic impediment.