Data from: Microsatellites reveal origin and genetic diversity of Eurasian invasions by one of the world's most notorious marine invader, Mnemiopsis leidyi (Ctenophora)

Marine invasions take place at an increasing rate. When occurring in blooms, zooplanktivorous comb jellies of the genus Mnemiopsis are able to cause pelagic regime shifts in coastal areas, and may cause the collapse of commercially important fish populations. Using microsatellites, developed for the first time in the phylum Ctenophora, we show that Mnemiopsis leidyi has colonized Eurasia from two source regions. Our preliminary data set included 4 sites within the putative source region (US East Coast and Gulf of Mexico), and 10 invaded locations in Eurasian waters. Bayesian clustering and phylogeographic approaches revealed the origin of earlier invasions of the Black and Caspian Sea in the 1980s / 1990s within or close to the Gulf of Mexico, while the 2006-invasion of the North and Baltic Seas can be directly traced to New England (pairwise FST = 0). We found no evidence for mixing among both gene pools in the invaded areas. While the genetic diversity (allelic richness) remained similar in the Baltic Sea compared to the source region New England, it was reduced in the North Sea, supporting the view of an initial invasion of Northern Europe to a Baltic Sea port. In Black / Caspian Sea samples, we found a gradual decline in allelic richness compared to the Gulf of Mexico-region, supporting a stepping-stone model of colonization with two sequential genetic founder events. Our data also suggest that current practises to reduce biological invasions via treatment of ballast water are insufficient to prevent repeated invasions of gelatinous zooplankton.

海洋生物入侵事件正以日益加快的速率发生。当Mnemiopsis属的栉水母（comb jellies）形成水华时，这类以浮游动物为食的类群可引发沿海区域的水层生态系统格局转变，甚至可能导致具有商业开发价值的鱼类种群崩溃。本研究针对栉水母动物门（Ctenophora）首次开发的微卫星标记（microsatellites），证实美胼栉水母（Mnemiopsis leidyi）已通过两个源种群区域成功入侵欧亚大陆。本研究的初步数据集涵盖了推测源区域内的4个采样点（美国东海岸与墨西哥湾），以及欧亚海域的10个入侵区域采样点。通过贝叶斯聚类（Bayesian clustering）与系统地理学分析方法，研究揭示：1980至1990年代入侵黑海与里海的早期种群，其起源地位于墨西哥湾区域或其邻近海域；而2006年入侵北海与波罗的海的种群则可直接追溯至新英格兰地区（两两FST值为0）。研究未在入侵区域内发现两类基因库发生混合的证据。与源种群区域新英格兰相比，波罗的海种群的遗传多样性（等位基因丰富度）保持相近水平，但北海种群的遗传多样性有所降低，这支持了北欧种群初始入侵路径为波罗的海港口的假说。相较于墨西哥湾区域种群，黑海与里海的样本等位基因丰富度呈现逐步下降的趋势，这支持了存在两次连续遗传奠基事件的踏脚石定殖模型。本研究数据同时表明，当前通过压载水处理以降低生物入侵的措施，不足以阻止胶质浮游动物的反复入侵。