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Title: Population genetic studies of the mussel Mytilus using nuclear DNA markers
Author: Silva, E. P. da
Awarding Body: University of Wales Swansea
Current Institution: Swansea University
Date of Award: 1998
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The genetics of the mussel Mytilus is one of the most extensively studied among the marine invertebrates. This work is concerned with the use of nuclear DNA polymorphisms to study aspects of Mytilus population genetics. Sixteen populations of three species, M. edulis, M. galloprovincialis and M. trossulus were studied for 6 nDNA markers. SSCP analysis was used to enhance the variability in the N118 anonymous scnDNA region, a PCR fragment which previously showed little RFLP variation, and in a second PCR product from a nrDNA internal transcribed spacer region. In the first case, the number of alleles increased from 4 to 7 and the FST estimate from 0.0072 to 0.0096. In the second case, four alleles were resolved and a statistically significant FST value of 0.08 was revealed. Also, primers for an intron of myosin heavy chain was developed and fifteen alleles were resolved. Three of the alleles are M. trossulus specific, but the others show significant frequency differences among different species and even among populations in the same species. Analysis of the nuclear DNA population structure in M. edulis showed statistical significant levels of geographic variation, and when compared with allozymes revealed significant differences between the two sets of markers. This result is consistent with the operation of balancing selection on allozymes. Moreover, the use of the Ewens-Watterson homozygosity test revealed for the nDNA polymorphism a departure from a strictly neutral model, indicating that assumptions about the neutrality of a DNA polymorphisms could also be under suspicion. Evolutionary relationships between the three mussel species using nDNA markers are in line with morphological and allozymes studies, which show M. edulis as more closely related to M. galloprovincialis than to M. trossulus. However, a much higher level of differentiation than previously reported was found between the three taxa.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available