Evolutionary drivers of invasion: hybridization and local adaptation in the Amazon sailfin catfish

Uncovering the mechanisms underlying rapid genetic adaptation can provide insights into adaptive evolution of invasive species. The armored catfish (Pterygoplichthys sp.) is an invasive species that has negative ecological impacts. Morphological and genetic data, based on mitochondrial DNA, suggested that armored catfish from the Grijalva-Usumacinta basins, Mexico, are hybrids. We used a double digest restriction-site associated DNA (ddRAD-seq) approach to gain understanding about the identity of the armored catfish of the Grijalva-Usumacinta River Basins, and to identify candidate loci that could be facilitating adaptation to environmental conditions in invaded areas. We sampled 103 armored catfish (Pterygoplichthys sp). We assembled a transcriptome to be used as reference for SNP calling. We performed de novo and transcriptome reference-based SNP calling (22,595 SNPs and 3,083 SNPs, respectively). High levels of genetic diversity (HE = 0.378 de novo, HE = 0.265 reference), heterozygotes excess (FIS = -0.0129 de novo, FIS = -0.429 reference) and low levels of genetic differentiation (FST = 0.0083 de novo and FST = 0.0086 reference), support the hypothesis of rapid dissemination and population expansion from a population of hybrid origin. We identified 54 candidate loci; of these, one relates to stress tolerance, and another to osmotic stress. Hybridization, high genetic variation and selection may play a relevant role in the invasion success of armored catfish. To control the populations of this invasive species, it is advisable to minimize habitat degradation and implement habitat restoration. Hybridization in aquariums and other facilities for its reproduction and commercialization should be prevented.