Estrutura genética de populações da piranha vermelha, Pygocentrus nattereri (Characiformes: Serrasalminae) com base no DNA mitocondrial e nuclear

Abstract

The red piranha, Pygocentrus nattereri, is an important resource for artisanal and commercial fisheries. The present study determines levels structure and genetic variability among populations of P. nattereri in basins hydrographic of Maranhão based on mitochondrial DNA sequences (rRNA 16S, COI e Control Region) and Nuclear (Microsatellites). The DNA was isolated using a standard phenolchloroform protocol and mitochondrial regions and microsatellite loci were amplified by PCR. The PCR products were sequenced using the didesoxyterminal method. For the 16S rRNA gene fragment was obtained from 576 pb, 23 haplotypes, һ= 0.950 e π= 0.004. The phylogenetic analysis grouped specimens with 99% to 100% of bootstrap. Genetic distances between and within populations varied from 0% to 1%. The sequencing of the COI gene resulted in a fragment of 672 bp, 23 haplotypes, һ= 0.940 e π= 0.009. The AMOVA indicated that most of the molecular variation (64%) arises between groups. The fixation index was highly significant (FST = 0.707, P < 0.00001). The phylogenetic analysis indicated that the specimens represent a monophyletic group. Genetic distances between populations varied from 0% to 2%, and were 0–1% within populations. For the Control Region was obtained 1040 pb, 41 haplotypes, һ= 0.978 e π= 0.009. The neutrality tests (D and Fs) were significant (P < 0.05) for most of the populations analyzed. The AMOVA indicated that most of the molecular variation (72%) arises between groups. The fixation index was highly significant (FST = 0.707, P < 0.00001). The phylogenetic analyses indicated that the specimens represented a monophyletic group. Genetic distances between populations varied from 0.8% to 1.9%, and < 0.5% within populations. The microsatellite primers amplified 104 alleles. The expected heterozygosity ranged 0.362 - 0.494 and observed heterozygosity ranged 0.438 - 0.510. The coefficient of inbreeding (FIS) showed an excess of heterozygotes (negative value f) for all loci analyzed (P < 0.05). The AMOVA indicated that most of the molecular variation (89%) arises within populations. The FST was 0.229 with highly significant p (<0.00001). The genetic distance between populations showed rates of variation of 0.009 (Mearim/Pindaré) to 0.580 (Parnaíba/Itapecuru). The degree of genetic differentiation found among the stocks of P. nattereri indicates the need for the development of independent management plans for the different river basins in order to preserve the genetic variability of their populations.