Desvendando processos atuais e históricos dos peixes migradores e sedentários: uma abordagem genômica, filogeográfica e genético-populacional entre as Bacias do Orinoco e Amazonas

Abstract

The Amazon and Orinoco rivers have the greatest diversity of fish fauna of the planet, which is estimated between 1300 - 3000 species. Much of this diversity is shared between them, but to respect there are no solid studies to support the spatial boundaries, time nor the mode of interaction of the ichthyofauna between the two river systems, preventing lay the scientific justification for its correct use for fishing and prioritization of conservation areas. In order to know the evolutionary history and current and historical population relationship between the shared fish fauna for the basins, in addition to the spatial configuration of its conservation units, a phylogeographic and population genomic/genetic approach was performed using eight species of highly exploited fish as model: Five migratory species (Brachyplatystoma rousseauxii, Colossoma macropomum, Piaractus brachypomus, Pseudoplatystoma metaense/P. tigrinum, Pseudoplatystoma orinocoense/P. punctifer) and three sedentary species (Nannostomus unifasciatus, Paracheirodon axelrodi, Pterophyllum altum). For that, the study was conducted in four stages, two for create some genomics tools for the analysis, and two in which was applied genetic and/or genomic tools to answer the initial population questions. First, it was standardized and characterized a methodology for genomic libraries construction for SNPs discovery and de novo genotyping in non-model species. Second, in order to verify the reproducibility and efficiency of the method in sequence tags discovery, genotyping, and utility for SNPs primer design, was used individuals of B. rousseauxii and C. macropomum as model. Third, mtDNA (Cytochrome oxidase I and Region control) and nuDNA (Glycosyltransferase and 6 alpha heavy chain of cardiac myosin) sequences were used to population genetic and phylogeographic analyzes in order to test the hypothesis of current and historical connectivity between basins. Fourth, the conservation units were defined (Evolutionary Significantly Units - ESUs, Adaptive Units - AUs and Management Units - MUs) including new evidence as multilocus analysis (Species trees), ecological data (pH and pluviosity) and genomic data. As a result, we obtained a compatible and efficient method for sequence reads production in IonTorrent PGM. The method was effective for tags discovery (18772-22476), de novo SNPs genotyping (268-398 SNPs) and for primer design in flanking regions of SNPs (23-39 SNPs). Population analysis showed a strong structure for all species between basins, but not within theme (except for sedentary fish). Of the eight species studied, only P. orinocoense/P. punctifer showed evidence of recent gene flow between basins, through the Casiquiare. Nevertheless, for all species, the nuDNA showed strong biological groups sharing between basins, suggesting that the divergence between these is recent. Coalescent analysis showed that only N. unifasciatus populations of Orinoco and Amazon diverged in the Pliocene, while the rest of the species diverged in the Pleistocene. In any case, there was not concordance with the vicariance hypothesis between basins generated by the Vaupés Arch in the Middle Miocene. The genetic, genomic and ecological evidence permitted to determine ESUs and MUs, but not AUs to any species. In most migratory fishes, the basins constituted a single ESU with independents MUs (C. macropomum, P. metaense/P. tigrinum, P. orinocoense/P. punctifer), but only to B. rousseauxii and P. brachypomus each basin were independents ESUs. For sedentary fish, was observed a greater number of ESUs compared with migratory fishes, wherein at least one of these units is shared between basins, while others were exclusives. This study demonstrates that the basins of the Orinoco and Amazon possessed a historical connectivity until the very recent past, and even today keeps this connection condition for part of their fish fauna.