Population genetic structure of the Amazonian black flannelmouth characin (Characiformes, Prochilodontidae: Prochilodus nigricans Spix & Agassiz, 1829): contemporary and historical gene flow of a migratory and abundant fishery species

Abstract

In the present study, sequences of the mtDNA control region (834 bp) were analyzed from 337 specimens of Prochilodus nigricans from sites along the main channel of the Amazonas River and three major tributaries, Madeira, Purus, and Juruá. The results of the analysis of molecular variance revealed that a large part of the genetic variation occurred within the populations analyzed (~85 %). Analysis with SAMOVA and Barriers suggested that the upper Madeira River and Purus Rivers had diverged genetically from the other samples, indicating restricted gene flow among these areas, while sites within the remaining range exhibited relatively little population structure. The high degree of structuring observed in the Madeira River basin population may be attributed to the presence of rapids along its upper course, while the genetic divergence found in the upper Purus River suggests historical connection between the upper Purus and upper Madeira Rivers followed by slow genetic drift due to large effective population sizes. However, given the life history and hypothesized evolutionary strategy of this species, we urge caution in interpreting that this targeted species is not at risk of overexploitation due to contemporary abundance. In order to preserve genetic diversity, we recommend enforcement of management regimes for regional stocks.