Genetic relationships among populations of Mytilus desolationis from Kerguelen, M edulis from the North Atlantic and M. gallo-provincialis from the Mediterranean

The mussel M w u s desolationis Lamy 1936, which constitutes large populations in the Kerguelen Islands, a highly isolated archipelago, is generally considered an endemic species on the basis of morphological data. Cross-matching of electromorphs of M. desolationis with those of M eduljs and M. galloprovinciaLis demonstrated that the 29 electromorphs recorded in M. desolahonis at 12 loci were identified in the 38 electromorphs observed in European populations at the same loci. Nine rare electromorphs are lacking in the Kerguelen mussel but no diagnostic locus was detected in the present study. Allozyrnic frequencies at 10 enzymahc loci from 2 populations of M. desolationis are analysed and compared with the data of Skibinslu et al. (1980Skibinslu et al. ( , 1983) on 4 populations of M. eduLis and 3 populations of M. galloprovmcialis. Correspondence analysis shows that 2 levels of allozymic frequency vanations can be distlngushed among the 9 populations: one level corresponding to a 'taxonomic' differentiation among these forms, the other corresponding to a population level within the taxa and more related to the environment. A phenogram illustrate< genetic re!zt;onships amcng h.l: dcso!;ci'oi;is, X. g & o p ~u v i ~~cialis and M. edulis, and the level of isolation of M. desolationis is discussed in terms of rare allozymes. Results suggest identification of M. desolationis as a semi-species in the super-species Mytilus edulis, inhabiting a low gene flow environment and subjected to high selective pressure.