Population genomics shed light on the demographic and adaptive histories of European invasion in the Pacific oyster, Crassostrea gigas

Crassostrea gigas originated from the Pacific coast of Asia but was introduced into several European countries in the early 1970s. Natural populations have now spread the length of the western seaboard of Europe. To elucidate the demographic and selective processes at play during this rapid expansion, genome-scan analysis was performed on different populations. High diversities and low differentiation were observed overall, but significant genetic differentiation was found among newly-established populations and between the newly-established northern group and a nearly panmictic group composed of southern European populations and a population from Japan. Loss of genetic diversity was also seen in the north, likely caused by founder events during colonisation. The few strongly supported outlier loci revealed a genetic structure uncorrelated with the north/south differentiation, but grouping two samples from the Danish Fjords (northern group) and one from the Dutch Scheldt estuary (southe...长牡蛎（Crassostrea gigas）原产于亚洲太平洋沿岸，于20世纪70年代初被引入多个欧洲国家。目前其自然种群已扩散至整个欧洲西部沿海区域。为阐明此次快速扩张过程中发挥作用的种群动态与选择性演化过程，研究人员对不同种群开展了基因组扫描分析。整体来看，观测到较高的遗传多样性与较低的遗传分化水平，但在新建种群之间，以及新建北部种群与由南欧种群及日本种群构成的近乎随机交配群之间，存在显著遗传分化。北部种群还出现了遗传多样性丢失现象，推测其由定殖过程中的奠基者效应所致。少数经强力支持的异常位点（outlier loci）揭示出一种与南北分化无关的遗传结构，该结构将丹麦峡湾的两份样本（归为北部种群）与荷兰斯海尔德河河口的一份样本（东南部…）归为一类。