Population genetic structure of mussels from the Baltic Sea |
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Authors: | H -P Bulnheim E Gosling |
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Institution: | (1) Biologische Anstalt Helgoland (Zentrale), Notkestr. 31, D-2000 Hamburg 52, Federal Republic of Germany;(2) Regional Technical College, Galway, and Zoology Department, University College, Galway, Ireland |
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Abstract: | In a macrogeographic survey, the population genetic structure of mussels from various regions of the Baltic Sea, a large semi-enclosed
brackish-water basin, was examined with reference toMytilus edulis andM. galloprovincialis samples from the North Sea, Irish coast and southern Portugal. Electrophoretically detectable variation was analysed at 6
polymorphic enzyme loci (Ap, Est-D, Lap-2, Odh, Pgi andPgm). Evidence was provided of a remarkably large amount of biochemical genetic differentiation among ecologically and morphologically
divergent mussel populations in the Baltic. Patterns of allele frequencies in low-salinity populations from the area of the
Baltic Proper were demonstrated to be widely homogeneous but contrast strongly with those of the western Baltic, the latter
resembling populations from marine habitats of the North Sea. Associated with a pronounced salinity gradient, the spatial
heterogeneity in gene-pool structure is indicated by steep clines of allele frequency changes in the area of the eastern Danish
isles. The adaptive significance of the observed allozymic variation is suggested. From genetic distance estimates, the subdivision
of population structure is discussed in relation to the significant amount of differentiation detected withinMytilus populations to date and to the evolutionary time required for the divergence of Baltic mussel populations. The allozymic
data provide evidence for the genetic distinctiveness of mussels from the low-salinity areas of the Baltic. Their position
at the specific or subspecific level of classification requires further consideration. |
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