Mitochondrial DNA variation in the European lobster ( Homarus gammarus) throughout the range
The genetic differentiation of the European lobster (Homarus gammarus) was investigated in 3,283 individuals from 44 population samples throughout its geographical distribution (Norway to Greece) by means of polymerase chain reaction restriction fragment length polymorphism analysis of a 3-kb mitochondrial DNA segment. Ninety composite haplotypes were revealed with the number of haplotypes in each population sample ranging from 4 to 31. Private haplotypes were found at very low frequencies. The global exact test of sample differentiation based on composite haplotype frequencies was statistically significant. FST analyses also showed significant heterogeneity among the European lobster population samples (FST=0.078, P<0.001). This differentiation was mainly due to the population samples from northern Norway, the Netherlands, and the Mediterranean Sea. These samples differentiated from the rest due to reduced gene diversity rather than to unique haplotypes. The relationships among these samples were illustrated with cluster analyses, four major distinct groups were evident: Mediterranean, northern Norway, Netherlands, and the remaining Atlantic samples. Based on the low degree of differentiation revealed in the European lobster and its limited capacity for dispersal, the most probable hypothesis is that all populations have been established from a common refuge after the end of the last Ice Age, that is, within the past 15,000 years. The results of this study show that mitochondrial DNA is a powerful tool for the determination of the genetic structure among lobster samples, which is important for a proper management policy designed to protect and to cultivate this species.