Diversidade de espécies de Geophagus Heckel, 1840 (Cichliformes: Cichlidae) da bacia amazônica utilizando abordagem genômica e de DNA mitocondrial

Abstract

The Neotropics are home to the largest community of freshwater fish in the world, knowing this diversity is important for the conservation of fish, especially those already exploited for commercial purposes, as is the case with species of the genus Geophagus. Many representatives of this genus are exploited by the national and international aquarium trade, but delimiting and quantifying species such as those of this genus can be a difficult task, since the group is considered specious and problematic in several taxonomic levels. Molecular approaches are being used in order to improve biodiversity estimates, and species discovery methods from single locus (SLSD) and multilocus have been complemented to improve these estimates. This study aims to: (i) investigate the diversity of Geophagus sensu stricto; (ii) map the species/lineages indicated with COI; (iii) test whether the COI data are corroborated with the SNPs data. To meet objectives (i and ii) the cytochrome c oxidase subunit I (COI) of 337 individuals sampled in 77 locations inside and outside the Amazon basin were sequenced. Four methods with different approaches for species delimitation from a single locus were used. The results showed six new morphologically distinct lineages that were corroborated by most of the SLSD methods, the numbers of lineages varied according to the method (15-mPTP; 14-LocMin; 18-bGMYC and 30-GMYC). For the mapping of the lineages, the bGMYC method was considered, since it was observed that it was the most consistent with the morphological data and also because it presents a spatial distribution pattern in accordance with what is known for other fish species. To meet objective (iii) 87 individuals were used to obtain genomic data, these individuals were representative of the 337 sequenced by COI, both in species diversity and in sampled locations. To obtain the SNPs, the ddRADs methodology was used, 15 million readings were obtained and 3757 SNPs were captured with a size greater than 200 bp. The taxonomic hypothesis tested was: which of the four delimitation methods (mPTP; LocMin; bGMYC and GMYC) is supported with the SNPs data? The results of the hypothesis tests showed that the GMYC method was the most supported by the genomic data. In addition to these tests, a phylogenetic comparison was performed by mirroring two trees, one obtained with SNPs and the other with COI. The results of the hypothesis tests showed that the GMYC method was the most supported by the genomic data. In addition to these tests, a phylogenetic comparison was performed by mirroring two trees, one obtained with SNPs and the other with COI. The results showed that both markers were not able to resolve the phylogenetic relationships of the species/lineages, however the COI recovered the monophyly of all species/lineages (except Geophagus sp. 5) and SNPS were not able to confirm the monophyly of the most species/strains. The SNPs data also showed signs of hybridization in some of the studied Geophagus species. Therefore, our results show a cryptic diversity, with putative species inhabiting areas threatened by anthropic activity and highlight the importance of combining mitochondrial and nuclear DNA data in biodiversity estimation studies, especially in taxonomically diverse tropical biotas.