Author:

Keywords:

Population genetics, Microsatellites, Range expansion, Non-native species, Aquaculture, Connectivity, Scandinavia, Skagerrak, Science & Technology, Life Sciences & Biomedicine, Physical Sciences, Ecology, Marine & Freshwater Biology, Oceanography, Environmental Sciences & Ecology, GENETIC DRIFT, POPULATION-STRUCTURE, NONNATIVE OYSTERS, MICROSATELLITE, ADAPTATION, SOFTWARE, EVENTS, 0405 Oceanography, 0602 Ecology, 0608 Zoology, Marine Biology & Hydrobiology, 3103 Ecology, 3109 Zoology, 4102 Ecological applications

Abstract:

© The authors 2017. Open Access under Creative Commons by Attribution Licence. Identifying the routes and rates of introductions is fundamental for the understanding of marine invasions. Recurring introductions over the last 50 yr have led to the establishment of feral Pacific oyster Crassostrea gigas populations throughout Europe. In the northern countries, Sweden and Norway, the species first occurred in large numbers in 2006. Here, we investigated the relative importance of introduction via re-laying of cultured oysters imported for consumption from France, Ireland or the Netherlands, and dispersal of oyster larvae by ocean currents from wild oyster populations in Denmark. Using microsatellite DNA markers, we estimated genetic differentiation among Pacific oysters collected at 4 Swedish locations, 3 Norwegian locations and 9 potential source locations in Denmark, Ireland, the Netherlands and France. All Swedish samples and 1 Norwegian sample (Tromlingene) were genetically similar to each other and the Danish samples and showed significant genetic differentiation from all other populations. Consequently, it appears that the Pacific oyster populations in Sweden, Denmark and Tromlingene are closely connected and/or share a recent origin. The 2 remaining Norwegian samples (Hui and Espevik) differed from each other and all other populations, but showed similarities to wild oyster samples from Scandinavia and Ireland, respectively. Overall, the results underline a complex origin of Norwegian oysters, with gene flow from Swedish/Danish populations, as well as other unidentified sources. The apparent connectivity among most of the Scandinavian populations has implications for regional management of this invasive species, and highlights possible scenarios for other marine invasive species with a similar life history.