Genetic variation in a newly established population of the Atlantic rock crab Cancer irroratus in Iceland

The Atlantic rock crab Cancer irroratus is native along the east coast of North America. The species was first recorded in Iceland in 2006 and has since rapidly spread throughout the country’s southwestern and western coastal waters. The transport of larvae in ballast water is the most probable route by which introduction into Iceland occurred. As this species is commercially valuable, it may be possible to establish a viable industry harvesting rock crabs in Iceland; however, to do this, more information on species-wide genetic diversity and demography is required. In this study, genetic variation at 7 microsatellite markers was analyzed in samples from Iceland and 5 sites in North America, capturing most of the known range of this species. Our results divided samples from the native range into 2 groups, divided by a previously proposed barrier to gene flow, compatible with local hydrographic factors restricting larval-mediated gene flow. The Icelandic population was markedly differentiated from all other samples, but exhibited comparable levels of genetic diversity with no evidence of small population effects or genetic bottlenecks. No single population could be identified as a source for the Icelandic population, though the likely origin could be attributed to the ‘northern group’ in the native range. Genetic data indicate that the number of founders of the Icelandic population was sufficient to retain genetic variation. As the Icelandic population shows evidence of self-recruitment and population expansion, it may represent a potential harvestable resource in Iceland