环境变化对水蚤群体遗传结构的影响

During the past century, most freshwater systems have been disturbed by human industrialization; especially, the anthropogenic eutrophication of freshwater lakes led to a significant decrease of biodiversity. In our previous studies, by using Daphnia as the model organism, we found that the temperature could effect the genetic structure of Daphnia populations, and the D. galeata prefer the eutrophicated water bodies. In our recent studies, we only detected D. galeata from D. longispina species complex in the eastern lakes of China, in contrast with previous survey which showed many taxa of this species complex were co-existed there. Our hypothesis is that the eutrophication of these eastern lakes resulted in an extremely decrease in biodiversity, only D. galeata from D. longispina species complex could be survive. Therefore, in present proposal, we will try to sample the diapausing eggs from sediment cores and hatch the D. longispina species complex in past century. Then, we will investigate the species shift during the last 100 years, also heir population structure. Finally, we will study the relationship between the taxon shift of D. longispina complex and the eutrophication. This study will help us to understand the impact of human-made ecological changes on the biodiversity in freshwater systems.

近百年来，人类活动严重干扰了淡水生态系统。特别是淡水湖泊的富营养化显著降低了其生物多样性。我们前期发现模式生物枝角类水蚤（Daphnia）的群体遗传结构可受温度等环境因子影响，且D. galeata适应于富营养化水体。近期，我们在40年前（节肢动物甲壳纲地理分布全国性调查）有长刺溞复合种多亚种共存的东部湖泊中仅检测到D. galeata。由此提出科学假设：长刺溞复合种中除D. galeata外绝大多数亚种因不能适应东部湖泊严重富营养环境而灭绝。本研究拟采集东部代表性湖泊中对应不同时期的底泥，分离和孵化水蚤长刺溞复合种休眠卵，重构过去百年不同时期的水蚤群体；利用线粒体全基因组和15个微卫星遗传位点，解析其群体遗传结构；分析不同时期长刺溞复合种的类群组成与对应时期湖泊富营养化指标的相关性。本研究有助于理解环境变化对淡水生态系统生物多样性的影响。

物种如何快速进化以适应环境是生物多样性研究的核心科学问题之一。近百年来，人类活动严重干扰了淡水生态系统。特别是淡水湖泊的富营养化显著降低了其生物多样性。在本轮自然基金面上项目支持下，我们以淡水浮游动物枝角类为研究对象，研究其分子系统发育、遗传多样性特征及快速进化，从而研究环境变化对淡水生态系统生物多样性的影响。取得了如下研究成果：①首次揭示中国枝角类代表物种分子系统发育关系、地理分布格局和群体遗传多样性特征，发现中国区域枝角类物种丰富且群体遗传多样性较高；②阐明了水体环境因子对枝角类水蚤群体遗传结构的影响；③阐明水蚤杂交是快速适应环境的重要策略之一，发现杂种无性生殖模式是其扩散形成优势类群的主因，解释了杂交对物种扩散的作用和其在新环境中定殖的机制。上述研究结果解析了我国浮游动物的生物多样性特征，阐明其应对变化环境的快速进化机制，对于维持我国健康淡水生态系统有着重要意义。