Genetic differences and environments of mussel populations in Kerguelen Islands

Summary Samples of subantarctic mussels, Mytilus desolationis, from 12 locations in the Kerguelen Islands (South Indian Ocean) were analysed electrophoretically at 5 polymorphic loci to study correlations between genotype frequencies and environmental factors. Thirty-one out 48 pairs (population-locus) were not in Hardy-Weinberg equilibrium proportions, and 41 out 60 showed heterozygote deficiency. Spatial heterogeneity analysed with correspondence analysis was observed at 3 loci (Lap2, Pgd and Pgm). The genetic differentiation of M. desolationis could be explained through both geographical origin of populations and adaptation to environmental conditions. Within each geographical group, the first parameter influencing spatial structure is salinity. Additional differentiation is related to a factor linked to maximal size and to a lesser extent to shore exposure. The higher genetic differentiation occurring within the Kerguelen populations than among continental populations could correspond to incomplete panmixia due to a reduced gene flow versus constant external immigration in continental populations.