由大尺度格局到边缘群体精密尺度格局的中国南北两种舌鳎群体遗传分化与适应性进化研究

Adaptability of marine fishes is the result of the long-term interaction of fish and complicated marine environment, which plays a quite important role in the process of evolution. However, it is poorly known about the relative importance and exact source of the adaptive evolution. Cynoglossus melampetalus and C. joyneri are two closely related species while possessing quite different ecological adaptation. These two species form a common habitat in the central coast of China, constituting the southern population of C. melampetalus and northern population of C. joyneri, respectively. Marginal population with highly ecological sensitivity and the relatively sessile tonguefish (survival of the fittest) is adopted as the perfect model to study the adaptive evolution of marine fish. The present study is based on these two tonguefish populations sampled both on a national coastal scale and small marginal population scale, and focuses on the marginal populations of two tonguefish inhabiting in the common environment. By using mitochondrial DNA and the newly developed 2b-RAD sequencing, the genome-wide nucleotide polymorphism among the populations will be scanned and determined, which is applied to evaluate the differentiation model and geography pattern. Multivariate ecological modeling approach, together with the geological history will be utilized to correlate the population’s divergence to assess the key environmental factors. By screening the genome for markers of neutral loci and outlier loci (selection pressure) among different populations, potential adaptive loci or genome regions under natural selection will be defined, which is aimed to reveal the geography pattern and mechanisms of adaptive evolution. These results could not only help to understand the evolutionary process and expanding mechanism of marine organism, but also provide scientific guidance for protection and utilization of tonguefish resources.

海洋鱼类适应性进化是鱼类与纷繁复杂的海洋环境长期互作的结果，在进化过程中扮演着十分重要的角色，但是目前人们对该部分进化力量的确切来源及其贡献度知之甚少。黑尾舌鳎和短吻红舌鳎是我国南北生态适应迥异的两种舌鳎，两者在中部沿海形成了一个共同分布区，分别构成了两种舌鳎的南缘和北缘群体。边缘群体生态敏感性和舌鳎相对固居习性（适者生存）构成了鱼类适应性进化研究的理想模型。本研究拟以两种舌鳎为对象，分别进行全国沿海-大格局和边缘群体精密尺度格局取样，聚焦共域边缘群体，采用线粒体和简化基因组测序技术对两种舌鳎进行群体基因组学研究，全面评估两种舌鳎群体分化模式和地理格局；利用多变量生态模型推测关键环境因子对群体分化的驱动作用；分析南北边缘群体可能受到的压力选择位点，从大尺度和精密尺度揭示两种舌鳎地理格局和适应性进化机制。该研究不仅有助于人们对海洋生物进化机制的认识，同时也为舌鳎资源的保护和利用奠定理论基础。

具有变温属性的海洋鱼类，其生活史始终直接暴露于复杂多变的海洋环境中，适应性进化似乎成为其与生俱来的生物特性。然而，生活在特殊环境下的海洋鱼类，其物种或者群体的分化是如何受海洋生境调控的？适应性和中性进化力量各自发挥了怎样的作用？其具体过程和作用机制又如何等，这些都是摆在人们面前悬而未决的科学难题。本项目以中国沿海南北两种舌鳎（黑尾舌鳎和短吻红舌鳎）为研究对象，采用线粒体、核糖体和简化基因组测序技术揭示两种舌鳎群体遗传结构、适应性进化过程及机制，成果如下：.1）整理和采集了我国沿海两种舌鳎12个地理群体共260余尾样品，根据形态及线粒体COI序列鉴定到种。.2）扩增测定了两种舌鳎线粒体基因组全序列及所有群体个体的线粒体基因片段，分析了两种舌鳎线粒体基因组序列特征及重排机制，发现黑尾舌鳎基因组具有独特的IMQψM重排现象，且首次提出舌鳎科线粒体IQM重排区间隔适用于舌鳎科系统发育研究，为研究鲽形目舌鳎鱼类的系统发育提供了珍贵的分子标记。.3）分析了两种舌鳎核糖体RNA基因序列多态性，为非协同进化提供了直接的分子证据，同时补充和修正了核糖体RNA假基因的鉴定标准，为假基因的定义及功能等提供了新的观点。.4）基于部分线粒体基因和2b-RAD简化基因组序列分析了两种舌鳎群体遗传结构，结果显示黑尾舌鳎和短吻红舌鳎分别呈现出两个和三个较明显的地理群体。利用BAYESCENV和LFMM两种方法对黑尾舌鳎进行适应性进化分析，两种方法共同筛选出6个受选择位点,通过与近缘种半滑舌鳎全基因组进行比对发现这些受选择的基因多与能量代谢和温度调节有关，推测黑尾舌鳎对不同海区温度适应性在其群体分化中扮演着重要角色。短吻红舌鳎结果类似，两种方法共同筛选出5个受选择位点，与半滑舌鳎全基因组比对发现其多与温度和渗透压调节有关。结果暗示海域温度和盐度等环境因子在两种舌鳎群体分化过程中扮演着重要角色。.该项目目前已发表SCI文章6篇，还有一篇小修审稿中；参加学术会议3人次；培养在读研究生3名。.