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.

海洋生物入侵的发生速率正持续攀升。当其形成水华时，隶属于侧腕栉水母属（Mnemiopsis）的浮游动物食性栉水母（comb jellies）可引发沿岸海域的浮游生态系统格局转变，甚至导致具有商业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），证实了侧腕栉水母（Mnemiopsis leidyi）从两个源种群区域入侵欧亚大陆。本研究的初步数据集涵盖了推测的源种群区域内的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，研究发现：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范围内或邻近海域；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F统计量（pairwise FST）=0）。研究未在入侵区域内发现两个基因库间存在基因交流的证据。相较于源种群区域新英格兰，波罗的海种群的遗传多样性（等位基因丰富度（allelic richness））未发生显著变化，但北海种群的遗传多样性有所降低，这一结果支持“北欧初始入侵路径为波罗的海港口”的假说。与墨西哥湾源种群区域相比，黑海与里海的采样种群的等位基因丰富度呈逐步降低的趋势，这支持“通过两次连续的遗传奠基者事件实现踏脚石式定殖”的模型。本研究数据同时表明，当前通过压舱水（ballast water）处理以防控生物入侵的措施，不足以阻止胶状浮游动物的重复入侵事件。