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Marine Biology

, Volume 137, Issue 3, pp 371–378 | Cite as

The relationship between allele frequency and tidal height in a mussel hybrid zone: a test of the differential settlement hypothesis

  • M. R. Gilg
  • T. J. Hilbish

Abstract

The blue mussels Mytilus edulis L. and M. galloprovincialis Lmk. hybridize in western Europe. Within hybrid populations nuclear alleles specific to M. galloprovincialis increase in frequency with age and size. This relationship changes with tidal height; alleles from M. galloprovincialis occur more frequently high in the intertidal zone, while M. edulis alleles predominate in the low intertidal zone. We tested the hypotheses that larvae with M. galloprovincialis alleles tend to settle higher in the intertidal zone, or that mussels redistribute themselves with respect to tidal height after initial larval settlement. We sampled recently metamorphosed mussels every 2 weeks in a hybrid mussel population at Whitsand Bay in southwest England throughout the summer of 1996. We observed four cohorts of newly settled mussels. There was no evidence of differential settlement of mussels with different genotypes in connection with tidal height, or into shaded versus unshaded microsites. Therefore, we rejected the preferential settlement hypothesis. There was substantial movement of juvenile mussels in the first 4 weeks following initial settlement, but this “secondary settlement” did not result in genetic differentiation with respect to tidal height. Further, significant differences in allele frequencies were found between primary and secondary spat. This allele frequency change was in the opposite direction of that seen in the adult population, suggesting newly settled larvae may be experiencing different selective pressures than adults. We propose that the genetic structure of hybrid mussel populations with respect to tidal height is the consequence of differences in selection intensity.

Keywords

Allele Frequency Intertidal Zone Hybrid Zone Blue Mussel Hybrid Population 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Springer-Verlag Berlin Heidelberg 2000

Authors and Affiliations

  • M. R. Gilg
    • 1
  • T. J. Hilbish
    • 1
  1. 1.Department of Biological Sciences, University of South Carolina, Columbia, South Carolina 29208, USA Fax: +1-803-7774002 e-mail: gilg@biol.sc.eduUS

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