title: Assessing patterns of hybridization between North Atlantic eels using diagnostic single-nucleotide polymorphisms.
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 (N=159) and from the neighboring Faroe Islands (N=29) 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 female × American eel male crosses, backcrosses were also detected, including a first-generation backcross (F1 hybrid × pure European eel) and three individuals identified as second-generation backcrosses originating from American eel × F1 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.
authors.affiliation: Department of Bioscience, Aarhus University, Aarhus C, Denmark.
authors.forename: J M
authors.initials: JM
authors.lastname: Pujolar
authors.affiliation: Department of Bioscience, Aarhus University, Aarhus C, Denmark.
authors.forename: M W
authors.initials: MW
authors.lastname: Jacobsen
authors.affiliation: 1] National Institute of Aquatic Resources, Technical University of Denmark, Silkeborg, Denmark [2] Department of Biomedicine-Human Genetics, Aarhus University, Aarhus C, Denmark.
authors.forename: T D
authors.initials: TD
authors.lastname: Als
authors.affiliation: Department of Bioscience, Aarhus University, Aarhus C, Denmark.
authors.forename: J
authors.initials: J
authors.lastname: Frydenberg
authors.affiliation: Faculty of Science and Technology, University of the Faroe Islands, Torshavn, Faroe Islands.
authors.forename: E
authors.initials: E
authors.lastname: Magnussen
authors.affiliation: Biopol, Marine Biology and Biotechnology Center, Skagastrond, Iceland.
authors.forename: B
authors.initials: B
authors.lastname: Jónsson
authors.affiliation: BGI-Shenzhen, Shenzhen, China.
authors.forename: X
authors.initials: X
authors.lastname: Jiang
authors.affiliation: BGI-Europe, Copenhagen Bio Science Park, Copenhagen, Denmark.
authors.forename: L
authors.initials: L
authors.lastname: Cheng
authors.affiliation: National Institute of Aquatic Resources, Technical University of Denmark, Silkeborg, Denmark.
authors.forename: D
authors.initials: D
authors.lastname: Bekkevold
authors.affiliation: 1] Laboratory of Biodiversity and Evolutionary Genomics, Deberiotstraat 32, University of Leuven (KU Leuven), Leuven, Belgium [2] Centre for Sustainable Tropical Fisheries and Aquaculture, School of Marine and Tropical Biology, James Cook University, Townsville, Queensland, Australia.
authors.forename: G E
authors.initials: GE
authors.lastname: Maes
authors.affiliation: IBIS (Institut de Biologie Intégrative et des Systèmes), Université Laval, Québec City, Québec, Canada.
authors.forename: L
authors.initials: L
authors.lastname: Bernatchez
authors.affiliation: Department of Bioscience, Aarhus University, Aarhus C, Denmark.
authors.forename: M M
authors.initials: MM
authors.lastname: Hansen
mesh_terms: D000818:Animals; D001267:Atlantic Ocean; D001947:Breeding; D019295:Computational Biology; D004272:DNA, Mitochondrial / Q000235:genetics; D004524:Eels / Q000235:genetics*; D005260:Female; D056426:Genetic Loci; D023281:Genomics; D005838:Genotype; D005843:Geography; D059014:High-Throughput Nucleotide Sequencing; D006824:Hybridization, Genetic; D007055:Iceland; D008297:Male; D020641:Polymorphism, Single Nucleotide
chemical_list: D004272:DNA, Mitochondrial