Rapid Evolution of the MH Class I Locus Results in Different Allelic Compositions in Recently Diverged Populations of Atlantic Salmon

• Published in: Molecular Biology and Evolution
• Main Authors: Consuegra, S., Megens, H.-J., Schaschl, H., Leon, K., Stet, R. J. M., Jordan, W. C.
• Format: Text
• Language: English
• Published: Oxford University Press 2005
• Subjects: Research Article; Atlantic salmon; Salmo salar
• Online Access: http://mbe.oxfordjournals.org/cgi/content/short/msi096v1; https://doi.org/10.1093/molbev/msi096

We compared major histocompatibility (MH) class I allelic diversity in two currently reproductively isolated Atlantic salmon ( Salmo salar ) populations (Irish and Norwegian) with a common post-glacial origin in order to test for among-population differences in allelic composition and patterns of recombination and point mutation. We also examined the evidence for adaptive molecular divergence at this locus by analysing the rate of amino acid replacement in relation to a neutral expectation. Contrary to our prediction, and in contrast to the situation for other genetic markers, the two populations have almost non-overlapping sets of MHC class I alleles. Although there is a strong signal of point mutation that predates population divergence, recent recombination, acting in similar, but not identical, ways in both populations appears to be a significant force in creating new alleles. Moreover, selection acting on peptide binding residues seems to favour new recombinant alleles and is likely to be responsible for the rapid divergence between populations.