中文摘要：

用流式分选结合末端限制性片段长度多态性的方法对长江中下游30个湖泊中超微型真核藻类的遗传多样性进行了研究,以了解不同环境条件下超微型真核藻类多样性的分布规律及其影响的主要因子.长江中下游湖泊大都已富营养化,但超微藻的群落组成差异仍然很大,T-RFLP分析共发现197个T-RFs,有45%的T-RFs（89个）仅在不到3个湖泊中检测到,聚类分析中各湖相似度均低于80%.中营养水平湖泊中多样性指数较高,总氮浓度与超微型真核藻类群落结构显著相关（P=0.006）,CCA分析中,第一轴与第二轴共解释了10.0%的超微型真核藻类群落组成的变化.本研究表明,湖泊中超微型真核藻类群落组成的环境异质性明显,其多样性与湖泊营养水平密切相关,此外其它非生物因素对其群落组成也可能存在重要影响.

英文摘要：

The genetic diversity of picoeukaryotic phytoplankton in the 30 lakes along the middle-lower reaches of the Yangtze River was studied using flow cytometry combined with terminal restriction fragment length polymorphism（T-RFLP）.The objectives of this study were to confirm the variance in the genetic diversity of picoeukaryotic phytoplankton among the lakes and to reveal its main affecting factors.Though the lakes investigated tended to or already were eutrophic,T-RFLP profiles of 18S rRNA gene fragments from picoeukaryotic phytoplankton showed high diversity.There were altogether 197 T-RFs detected from the lakes that we investigated,with 89 of them obtained in less than 3 lakes.Cluster analysis indicated their similarity was lower than 80%.Shannon-wiener diversity index showed that mesotrophic lakes contained more diverse picoeukaryotic phytoplankton community than eutrophic lakes.The canonical correspondence analysis revealed that the concentration of the total nitrogen had the most important impact on the picoeukaryotic phytoplankton communities（P = 0.006）.The results showed that the genetic diversity of picoeukaryotic phytoplankton in the lakes were of great environmental heterogeneity and closely related to the trophic status.Two CCA axes can only explain 10.0% of the total variance in picoeukaryotic phytoplankton composition,suggesting that the evolution of picoeukaryotic phytoplankton was probably connected to the top-down manipulation as well.