Genética populacional do bagre amazônico Pseudoplatystoma punctifer (Siluriformes: Pimelodidae) nas sub-bacias dos rios Madeira e Mamoré/Guaporé

Abstract

The great catfish Pseudoplatystoma punchier (surubim) is among the five species of catfish of the Amazon basin with greater commercial value. It plays important role as top predator in freshwater ecosystems of the Amazon. The movement of aquatic species, in watersheds, can be interrupted by natural biogeographic barriers, formed by rapids and waterfalls that produce distinct biota.There are clear differences between the biota (assemblies) of fish in the area that is upstream and downstream of the falls of the Madeira Rive. The waterfalls of Madeira River delimit two distinct regions: upstream the sub-basins of the Mamore/Guapore (which will be called the Mamore/Guapore sub-basin) and downstream the sub-basin of the Madeira River.The knowledge of how the life cycle of P. punchier is influenced by the Madeira River rapids and waterfall, taking into account their migratory route and how much genetic variation occurs in this species, within and between sub-basins, is very important for the conservation and for possible management measures. Molecular analyzes were performed by sequencing the COI gene of mtDNA and 10 microsatellite loci. Our objective was to determine whether P. punchier constitutes a parunitic population or if there is some kind of genetic segregation, associated with space and time, which can be related to the waterfalls of the river Madeira or the homing behavior. Were analyzed 96 specimens with the COI gene and 99 with microsatellite loci from six localities, being two in the the Mamore/Guapore sub-basin and four in the sub-basin of the Madeira River, both in the Amazon basin. With the COI marker were observed 11 haplotypes, a haplotype diversity of 0.600 and a nucleotide diversity of 0.00157. All analyzed microsatellite loci were highly polymorphic, the number of alleles per locus ranging from two (Ppu8) to 22 (Ppu4), on average 10.4 alleles per locus. The total number of observed alleles was 104, with 27 unique alleles. Based on the results of the analysis of molecular variance (AMOVA) and gene flow (Nm) observed between the sub-basins to the microsatellite (PST = 0.067; Nm= 6.883) and for the gene COI ((DST = 0.391; Able 0.643), we cannot reject the hypothesis of panmixia for Pseudoplatystoma punchier. However, it was evidenced that the specimens of P. punchier of Madeira River and Mamore/Guapore sub-basins feature a large genetic differentiation and intermediate for the gene COI and microsatellites, respectively. Genetic differentiation observed in Bayesian analysis of BAPS, with the COI data clearly showed the existence of two maternal lines, an in each sub-basin. This result may be related to: sedentary females; the different environmental conditions; the water regime of the Madeira River and Mamore/Guapoth sub-basins and with rapids and waterfalls and of the Madeira River, which partially disrupt the gene flow. We propose a model of migration of males on the basis of the results of the analysis of microsatellite loci and prior studies of ecology. Our results indicated the occurrence of two fishing stocks, which require separate management or priority for conservation. However, anthropogenic actions in the area of study, such as: the construction of dams, deforestation and the fishing exploitation, make the complex conservation and management measures.