Genetic structure of Norway lobster, Nephrops norvegicus (L.) (Crustacea :Nephropidae), from the Mediterranean Sea

The population genetic structure of the Mediterranean Norway lobster was st udied by means of cellulose acetate allozyme electrophoresis. Populations f rom one Atlantic and eight Mediterranean localities were sampled. The 15 en zyme systems analysed gave 23 presumptive gene loci, 11 of which were polym orphic. The analysis of genotypic and allelic frequencies revealed levels o f genetic polymorphism comparable with those of studied decapods: mean hete rozygosities ranged from 0.052 (se 0.025) to 0.142 (se 0.040). The values o f Nei's genetic distance index showed moderate genetic differentiation betw een geographical regions and no geographical pattern of genetic differentia tion was detected by UPGMA cluster analysis. Moreover no clear dines in all elic frequencies were detected, thus genetic variability seems to be random ly distributed among populations and Nephrops norvegicus seems to follow th e island model of genetic structure. The degree of genetic subdivision of t he species is confirmed by the mean value of the standardised variance in a llelic frequencies (F-ST = 0.122), giving an estimate of gene flow, Nm = 1. 80.