Genetic and ecological characterization of the invasive freshwater jellyfish Craspedacusta sowerbii

人口流动性和连通性增强的一个后果是，越来越多的非本地物种被引入生态系统。以非本地淡水水母Craspedacusta sowerbii为例，这一物种的引入在淡水浮游生物群落中创造了一个新的功能协会，因为数百万年来水母在欧洲湖泊群落中没有代表。淡水水母Craspedacusta sowerbii （Lankester 1880）起源于亚洲（中国），大约100年前就在德国湖泊中出现了。今天至少有100个不同地点的记录是已知的，根据现有的知识，种群中的水母是单性的，并且被认为是基因相同的，这表明只有一个或几个成功的克隆传播。Craspedacusta sowerbii有一个生生和浮游生物的生命周期，包括一个小的（1-2毫米）底栖水螅无性繁殖。根据对水母（1-2厘米大小）的观察，梭氏弧菌可能已经分布得更广了。小息肉通常不被注意，自由游动的水母阶段的大量发生的记录占主导地位。在一定的水温以上，珊瑚虫可以释放水母到外皮。因此，预测水温的升高会导致水母分布的快速增加。因此，随着观察到的个体数量达到1000 ind/m-2，水母对水生食物网动态的影响是可以预期的，但尚未详细说明。在实验室实验中，将确定肉食性水母的食物选择、同化和摄食效率，为与其他浮游生物的竞争提供基本信息。沿着水母丰度梯度的野外中生态实验将研究水母的营养位置，向下到浮游植物的级联效应以及水母介导的中上层-底栖能量和物质通量。此外，实地调查将调查和比较有水母或没有水母的湖泊中上层食物网的动态。实地调查将允许分析性别、基因型和环境之间的关系，并将有助于回答有关水母长期建立和进化动力学的问题。利用高分辨率微卫星和ITS、COI标记对苏氏螺旋藻的遗传多样性和群体结构进行研究。遗传分析将显示在息肉中是否存在不同的基因型，从而在水母阶段，是否只有一个克隆占主导地位，或者是否可能有多个引入。通过对该物种遗传多样性和生态功能的综合分析，可以更好地了解外来物种入侵下水生食物网的因果关系。

A consequence of the increasing mobility and connectivity of human populations is the rising introduction of non-native species into ecosystems. In case of the non-native freshwater jellyfish Craspedacusta sowerbii the introduction of this species created a new functional guild within freshwater plankton communities, as jellyfish were not represented in European lake communities for millions of years. The freshwater jellyfish Craspedacusta sowerbii (Lankester 1880) is originating from Asia (China) and known to be present in German lakes since about 100 years. Today records from at least 100 different locations are known and according to available knowledge jellyfish within populations are unisexual and assumed to be genetically identical suggesting the spread of only one or few successful clones. Craspedacusta sowerbii has a metagenetic and meroplanktonic life cycle, including a small (1-2 mm) benthic polyp reproducing asexually. C. sowerbii may be already far more distributed as suggested by observation of medusae (1-2 cm in size). The small polyp may often be unnoticed and records of mass occurrences of the free-swimming medusoid stage predominate. Above a certain water temperature polyps can release medusae into the pelagial. Predicted increasing water temperatures can therefore result in a fast increase of the distribution of medusae. Hence, with observed individual numbers up to 1000 ind/m-2 effects of medusae on aquatic food web dynamics are expectable but not specified in detail yet. In laboratory experiments food selectivity, assimilation and ingestion efficiencies of the carnivore jellyfish will be determined, giving basic information on competitiveness with other planktivorous organism. Field mesocosm experiments along jellyfish abundance gradients will investigate trophic positions of jellyfish, cascading effects down to phytoplankton and pelagic-benthic fluxes of energy and matter mediated by jellyfish. Additionally, field surveys will investigate and compare pelagic food web dynamics in lakes containing jellyfish or not. The field surveys will allow to analyse the association between sex, genotype and environment and will help to answer questions regarding long-time establishment and evolutionary dynamics of jellyfish. Genetic diversity and population structure of C. sowerbii will be studied using high-resolving microsatellites and ITS and COI markers. Genetic analyses will show if different genotypes are present in the polyp and consequently in the medusoid stage, if only one clone is dominant or if multiple introductions are likely. The combined analyses of the genetic diversity and the ecological function of this species will allow a better understanding of cause and effect relationships within aquatic food webs exposed to invasion by non-native species.