Address from 1/1/2005: Department of Biology, University of Turku, FIN-20014, Finland.
Distribution of genetic variation in the growth hormone 1 gene in Atlantic salmon (Salmo salar) populations from Europe and North America
Article first published online: 15 NOV 2004
Volume 13, Issue 12, pages 3857–3869, December 2004
How to Cite
RYYNÄNEN, H. J. and PRIMMER, C. R. (2004), Distribution of genetic variation in the growth hormone 1 gene in Atlantic salmon (Salmo salar) populations from Europe and North America. Molecular Ecology, 13: 3857–3869. doi: 10.1111/j.1365-294X.2004.02370.x
- Issue published online: 15 NOV 2004
- Article first published online: 15 NOV 2004
- Received 30 June 2004; revision received 9 September 2004; accepted 9 September 2004
- ascertainment bias;
- local adaptation;
- neutral evolution;
- single nucleotide polymorphisms
The level and hierarchical distribution of genetic variation in complete sequences of the Atlantic salmon (Salmo salar) growth hormone (GH1) gene were investigated in populations from Europe and North America with a view to inferring the major evolutionary forces affecting genetic variation at this locus. Seventeen polymorphic sites were identified in complete sequences from nine populations, with levels of noncoding (intron and untranslated region sequences) nucleotide diversity being similar to those observed in other species. No variation, however, was observed in exonic sequences, indicating that nucleotide diversity in the Atlantic salmon GH1 gene is three and 25 times less than that estimated for human and Drosophila coding sequences, respectively. This suggests that purifying selection is the predominant contemporary force controlling the molecular evolution of GH1 coding sequences. Comparison of haplotype relationships within and between populations indicated that differentiation between populations from Europe and North America was greater than within-continent comparisons. However, several haplotypes observed in the northernmost European populations were more similar to those observed in North American than to any other haplotypes observed in Europe. This is most likely to be a result of historical, rather than contemporary, gene flow. Neutrality test statistics, such as Tajima's D, were significantly positive in the European populations in which North American-like haplotypes were observed. Although a positive Tajima's D is commonly interpreted as the signal of balancing selection, a more likely explanation in this case is that either historical migration or ascertainment bias, rather than within population local adaptation, has given rise to an excess of intermediate frequency alleles.