title: Speciation and demographic history of Atlantic eels (Anguilla anguilla and A. rostrata) revealed by mitogenome sequencing.
abstract: Processes leading to speciation in oceanic environments without obvious physical barriers remain poorly known. European and American eel (Anguilla anguilla and A. rostrata) spawn in partial sympatry in the Sargasso Sea. Larvae are advected by the Gulf Stream and other currents towards the European/North African and North American coasts, respectively. We analyzed 104 mitogenomes from the two species along with mitogenomes of other Anguilla and outgroup species. We estimated divergence time between the two species to identify major events involved in speciation. We also considered two previously stated hypotheses: one where the ancestral species was present in only one continent but was advected across the Atlantic by ocean current changes and another where population declines during Pleistocene glaciations led to increasing vicariance, facilitating speciation. Divergence time was estimated to ∼3.38 Mya, coinciding with the closure of the Panama Gateway that led to reinforcement of the Gulf Stream. This could have advected larvae towards European/North African coasts, in which case American eel would be expected to be the ancestral species. This scenario could, however, not be unequivocally confirmed by analyses of dN/dS, nucleotide diversity and effective population size estimates. Extended bayesian skyline plots showed fluctuations of effective population sizes and declines during glaciations, and thus also lending support to the importance of vicariance during speciation. There was evidence for positive selection at the ATP6 and possibly ND5 genes, indicating a role in speciation. The findings suggest an important role of ocean current changes in speciation of marine organisms.
authors.affiliation: Department of Bioscience, Aarhus University, Aarhus C, Denmark.
authors.forename: M W
authors.initials: MW
authors.lastname: Jacobsen
authors.affiliation: Department of Bioscience, Aarhus University, Aarhus C, Denmark.
authors.forename: J M
authors.initials: JM
authors.lastname: Pujolar
authors.affiliation: Centre for GeoGenetics, Natural History Museum of Denmark, University of Copenhagen, Copenhagen, Denmark.
authors.forename: M T P
authors.identifier: 0000000258057195
authors.initials: MT
authors.lastname: Gilbert
authors.affiliation: Centre for GeoGenetics, Natural History Museum of Denmark, University of Copenhagen, Copenhagen, Denmark.
authors.forename: J V
authors.initials: JV
authors.lastname: Moreno-Mayar
authors.affiliation: Département de Biologie, Institut de Biologie Intégrative et des Systèmes (IBIS), Pavillon Charles-Eugène-Marchand, Québec, Québec Canada.
authors.forename: L
authors.initials: L
authors.lastname: Bernatchez
authors.affiliation: 1] Department of Biomedicine-Human Genetics, Aarhus University, Aarhus C, Denmark [2] National Institute of Aquatic Resources, Section for Marine Living Resources, Technical University of Denmark, Silkeborg, Denmark.
authors.forename: T D
authors.initials: TD
authors.lastname: Als
authors.affiliation: Javier Lobon-Cervia, National Museum of Natural Sciences (CSIC), C/ José Gutierrez Abascal, Madrid, Spain.
authors.forename: J
authors.initials: J
authors.lastname: Lobon-Cervia
authors.affiliation: Department of Bioscience, Aarhus University, Aarhus C, Denmark.
authors.forename: M M
authors.initials: MM
authors.lastname: Hansen
mesh_terms: D000811:Anguilla / Q000145:classification / Q000235:genetics*; D000818:Animals; D001267:Atlantic Ocean; D049810:Genetic Speciation; D054629:Genome, Mitochondrial; D008957:Models, Genetic; D008969:Molecular Sequence Data; D011156:Population Density; D012641:Selection, Genetic; D017422:Sequence Analysis, DNA; D014872:Water Movements