Author:

Keywords:

admixture analysis, anguilla, hybridization, RAD sequencing, SNPs, Science & Technology, Life Sciences & Biomedicine, Ecology, Evolutionary Biology, Genetics & Heredity, Environmental Sciences & Ecology, WESTSLOPE CUTTHROAT TROUT, ANGUILLA-ANGUILLA, EUROPEAN EEL, SARGASSO SEA, GENE-FLOW, HYBRIDS, INTROGRESSION, SPECIATION, RAINBOW, GENOME, Animals, Atlantic Ocean, Breeding, Computational Biology, DNA, Mitochondrial, Eels, Female, Genetic Loci, Genomics, Genotype, Geography, High-Throughput Nucleotide Sequencing, Hybridization, Genetic, Iceland, Male, Polymorphism, Single Nucleotide, 0603 Evolutionary Biology, 0604 Genetics, 3104 Evolutionary biology, 3105 Genetics

Abstract:

The two North Atlantic eel species, the European eel (Anguilla anguilla) and the American eel (Anguilla rostrata), spawn in partial sympatry in the Sargasso Sea, providing ample opportunity to interbreed. In this study, we used a RAD (Restriction site Associated DNA) sequencing approach to identify species-specific diagnostic single-nucleotide polymorphisms (SNPs) and design a low-density array that combined with screening of a diagnostic mitochondrial DNA marker. Eels from Iceland (N¼159) and from the neighboring Faroe Islands (N¼29) were genotyped, along with 94 larvae (49 European and 45 American eel) collected in the Sargasso Sea. Our SNP survey showed that the majority of Icelandic eels are pure European eels but there is also an important contribution of individuals of admixed ancestry (10.7%). Although most of the hybrids were identified as F1 hybrids from European eel femaleAmerican eel male crosses, backcrosses were also detected, including a first-generation backcross (F1 hybridpure European eel) and three individuals identified as second-generation backcrosses originating from American eelF1 hybrid backcrosses interbreeding with pure European eels. In comparison, no hybrids were observed in the Faroe Islands, the closest bodies of land to Iceland. It is possible that hybrids show an intermediate migratory behaviour between the two parental species that ultimately brings hybrid larvae to the shores of Iceland, situated roughly halfway between the Sargasso Sea and Europe. Only two hybrids were observed among Sargasso Sea larvae, both backcrosses, but no F1 hybrids, that points to temporal variation in the occurrence of hybridization.