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.

海洋生物入侵事件的发生频率正持续攀升。当其形成水华时，球栉水母属（Mnemiopsis）的浮游动物食性栉水母可引发沿海海域的浮游生态系统格局转型，甚至可能导致具有商业开发价值的鱼类种群崩溃。本研究使用首次在栉水母动物门（Ctenophora）中开发的微卫星标记（microsatellites），证实莱特氏球栉水母（Mnemiopsis leidyi）从两个源头区域入侵并定殖至欧亚大陆。本研究的初步数据集涵盖了推定源头区域内的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（phylogeographic analysis）方法，研究发现上世纪80至90年代入侵黑海与里海的早期种群，其源头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（成对FST值（pairwise FST）=0）。研究未发现入侵区域内两个基因库之间存在基因混合的证据。与源头区域新英格兰相比，波罗的海种群的遗传多样性（等位基因丰富度，allelic richness）保持相近水平，但北海种群的遗传多样性有所降低，这支持了北欧初始入侵事件始于波罗的海港口的推论。对黑海与里海的采样样本分析显示，与墨西哥湾区域相比，其等位基因丰富度呈逐步降低的趋势，这支持了存在两次连续遗传奠基者事件（founder events）的踏脚石定殖模型（stepping-stone model）。本研究数据同时表明，当前通过压载水（ballast water）处理以防控生物入侵的相关举措，不足以阻止凝胶状浮游动物（gelatinous zooplankton）的反复入侵。