Análise da variabilidade genética do peixe ornamental carnegiella strigata (characiformes, gasteropelecidae) de três rios de água preta da Amazônia central

Abstract

Ornamental fish species of the genus Carnegiella are commonly known as hatchetfish and in particular, Carnegiella strigata is known as the marbled hatchetfish. It is found in Guiana, Suriname, Colombia, Bolivia, Peru and Brazil (Amazon basin) and apparently is limited to black waters rivers. The present study is a preliminary assessment of the genetic variability of C. strigata from three black waters rivers in the Central Amazon. Sixty-nine specimens from five localities in the Negro river basin, one locality in the Urubu river basin and two localities in the Uatumã river basin were genotyped using the nucleotide sequence of mitochondrial ATPase 6/8 genes (646 bp). The mtDNA data resulted in unexpected high levels of variation that suggest the presence of more than only one evolutionary unit. Specimens from Mauá, Urubaxi, Pixirituba, Tarumã (Negro basin) and Urubu (Urubu basin) formed one evolutionary unit, and specimens from Barretinho and Uatumã (Uatumã basin) and Cajarizinho (Negro basin) formed another unit. Analyses of mitochondrial gene trees (maximum parsimony, maximum likelihood and genetic distance) and population genetics (DNA polymorphism, AMOVA, Mantel Test) allowed the identification of 13 haplotypes assembled in two monophyletic groups, with genetic segregation between them. The range of the genetic distance found in each evolutionary unit of the so-called C. strigata were distinct, and the average genetic distance between the evolutionary units was 11.50%. When compared to C. marthae, the sister species of C. strigata, both units showed an average genetic distance of 19.70%. Based on molecular data we suggest a past connection between the headwaters of some tributaries from the Negro and the Uatumã river basins. If we assume that each evolutionary unit detected corresponds to a valid species, then today, what is known as C. strigata in fact corresponds to a widespread species complex. If we assume that each evolutionary unit corresponds to a group of specimens which are genetically divergent and reproductively isolated from other groups of the same species, then the concept of an evolutionary significant unit (ESU) must be evoked.