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Open Access Highly Accessed Research article

Do North Atlantic eels show parallel patterns of spatially varying selection?

Malene G Ulrik1, José Martín Pujolar1, Anne-Laure Ferchaud1, Magnus W Jacobsen1, Thomas D Als23, Pierre Alexandre Gagnaire4, Jane Frydenberg1, Peder K Bøcher1, Bjarni Jónsson5, Louis Bernatchez6 and Michael M Hansen1*

Author Affiliations

1 Department of Bioscience, Aarhus University, Ny Munkegade 114, Bldg. 1540, DK-8000 Aarhus C, Denmark

2 National Institute of Aquatic Resources, Technical University of Denmark, Vejlsøvej 39, DK-8600 Silkeborg, Denmark

3 Department of Biomedicine-Human Genetics, Aarhus University, DK-8000 Aarhus C, Denmark

4 ISEM (Institut des Sciences de l’Evolution Montpellier), Université Montpellier II, 34095 Montpellier, France

5 Biopol, Marine Biology and Biotechnology Center, Einbúastígur 2, IS545 Skagastrond, Iceland

6 IBIS (Institut de Biologie Intégrative et des Systèmes), Université Laval, G1V 0A6 Québec, Canada

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BMC Evolutionary Biology 2014, 14:138  doi:10.1186/1471-2148-14-138

Published: 20 June 2014

Abstract

Background

The two North Atlantic eel species, the European and the American eel, represent an ideal system in which to study parallel selection patterns due to their sister species status and the presence of ongoing gene flow. A panel of 80 coding-gene SNPs previously analyzed in American eel was used to genotype European eel individuals (glass eels) from 8 sampling locations across the species distribution. We tested for single-generation signatures of spatially varying selection in European eel by searching for elevated genetic differentiation using FST-based outlier tests and by testing for significant associations between allele frequencies and environmental variables.

Results

We found signatures of possible selection at a total of 11 coding-gene SNPs. Candidate genes for local selection constituted mainly genes with a major role in metabolism as well as defense genes. Contrary to what has been found for American eel, only 2 SNPs in our study correlated with differences in temperature, which suggests that other explanatory variables may play a role. None of the genes found to be associated with explanatory variables in European eel showed any correlations with environmental factors in the previous study in American eel.

Conclusions

The different signatures of selection between species could be due to distinct selective pressures associated with the much longer larval migration for European eel relative to American eel. The lack of parallel selection in North Atlantic eels could also be due to most phenotypic traits being polygenic, thus reducing the likelihood of selection acting on the same genes in both species.

Keywords:
Adaptation; European eel; Genetic-by-environment associations; Parallel selection; Single nucleotide polymorphisms