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Genes (Basel). 2020 Jan 17;11(1). pii: E109. doi: 10.3390/genes11010109.

Population Genomics in Rhamdia quelen (Heptapteridae, Siluriformes) Reveals Deep Divergence and Adaptation in the Neotropical Region.

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Sección Genética Evolutiva, Facultad de Ciencias, UdelaR, Iguá 4225, Montevideo 11400, Uruguay.
Departamento de Zoología, Genética y Antropología Física, Facultad de Veterinaria, Campus de Lugo, Universidade de Santiago de Compostela, Avenida Carballo Calero s/n, E-27002 Lugo, Spain.
Instituto de Acuicultura, Universidade de Santiago de Compostela, Campus Vida s/n, E-15782 Santiago de Compostela, Spain.


Rhamdia quelen, a Neotropical fish with hybridization between highly divergent mitochondrial DNA (mtDNA) lineages, represents an interesting evolutionary model. Previous studies suggested that there might be demographic differences between coastal lagoons and riverine environments, as well as divergent populations that could be reproductively isolated. Here, we investigated the genetic diversity pattern of this taxon in the Southern Neotropical Basin system that includes the La Plata Basin, Patos-Merin lagoon basin and the coastal lagoons draining to the SW Atlantic Ocean, through a population genomics approach using 2b-RAD-sequencing-derived single nucleotide polymorphisms (SNPs). The genomic scan identified selection footprints associated with divergence and suggested local adaptation environmental drivers. Two major genomic clusters latitudinally distributed in the Northern and Southern basins were identified, along with consistent signatures of divergent selection between them. Population structure based on the whole set of loci and on the presumptive neutral vs. adaptive loci showed deep genomic divergence between the two major clusters. Annotation of the most consistent SNPs under divergent selection revealed some interesting candidate genes for further functional studies. Moreover, signals of adaptation to a coastal lagoon environment mediated by purifying selection were found. These new insights provide a better understanding of the complex evolutionary history of R. quelen in the southernmost basin of the Neotropical region.


RAD-seq; Rhamdia quelen; environmental adaptation; genomic divergence

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