MEPS 156:225-237 (1997)  -  doi:10.3354/meps156225

Heterozygote deficiency in the mussel Mytilus edulis species complex revisited

Michel Raymond1,2,*, Roisi L. Vääntö3, Fréderic Thomas4, François Rousset1, Thierry de Meeüs4, François Renaud4

1Institut des Sciences de l'Evolution (UMR CNRS 5554), Laboratoire Génétique et Environnement, Université de Montpellier II (CC 065), F-34095 Montpellier Cedex 05, France
2Department of Genetics, Uppsala University, Box 7003, S-75007 Uppsala, Sweden
3Zoological museum, SF-00100 Helsinki, Finland
4Laboratoire de Parasitologie Comparée (UMR CNRS 5555), Université de Montpellier II (CC 105), F-34095 Montpellier Cedex 05, France
*Address for correspondence: Laboratoire Génétique et Environnement, Université de Montpellier II (CC 065), F-34095 Montpellier Cedex 05, France.

In order to understand the phenomenon of heterozygote deficiency (Fis) in marine molluscs, all the relevant literature concerning this phenomenon in the Mytilus edulis species complex was reviewed. Due to large heterogeneity in methods of data analysis, in particular for the choice of the estimator measuring heterozygote deficiency and for the choice of the testing procedure, no clear overview was possible. To overcome this problem, similar estimators and tests were used to analyze or re-analyze some additional large data sets from the Baltic (M. trossulus), France (M. galloprovincialis), England (M. edulis), Atlantic USA (M. edulis) and Pacific USA (M. trossulus). Large and significant heterozygote deficiencies exist in these data sets. Estimated Fis (F-hatis) values are generally higher for Lap than for other loci, consistent with an effect of selection. No other significant variation of F-hatis values across loci within each data set or across data sets for each locus was detected, however no specific test has been designed for this null hypothesis. The possible contribution of a Wahlund effect to explain the heterozygote deficiency is discussed. It is likely that there is no unique explanation of heterozygote deficiency (such as a Wahlund effect or selection) in M. edulis or in other organisms, and that species-specific, locus-specific or population-specific explanations are to be sought.

Mytilus · Population genetics · Heterozygote deficiency · Allozyme

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