基于种群基因组学的两种浅海底栖生活蛸科动物的谱系地理格局与适应性分化研究

Adaptive differentiation is one of the most important strategies for marine organisms to respond to environmental changes, and this is especially true when it comes to the relatively sessile marine benthos. However, the adaptive differentiation in marine organisms, together with its role in responding to environmental changes has been largely ignored for a long term. The present study will use two relatively sessile benthic octopus species, Octopus variabilis and O. ocellatus, inhabiting the highly heterogeneous epibenthic environment along the coast of China, as the model animals to investigate how the adaptive evolution will contribute to the differentiation and hence the speciation of marine populations. By scanning through the whole mitochondrial and nuclear genome using the newly developed population genomic technologies based on mitochondrial DNA and RAD sequencing, the genome wide nucleotide polymorphism among the populations will be determined and used ,when incorporated together with the morphologic information, to evaluate the phylogeographical differentiation among the populations and to identify the possible cryptic or subspecies speciation among the lineages. Demographic history analyses will be utilized to evaluate the evolution history of the populations, and to assess the potential impact of the historical geographical events on the speciation of the octopus populations. Multivariate ecological modeling approach will be applied to correlate the population’s divergence with the spatial environment heterogenicity among the ecotypes, and to define the key environmental factors, which drives the differentiation. By screening the genome for markers that have normal (neutral loci) and extreme levels of differentiation (outlier loci) between ecotypes, phenotypes or populations, potential adaptive loci or genome regions under natural selection will be defined, and the role of it plays in the population divergence and the possible factors which drives the adaptive variation will be determined. By involving both of the neutral and adaptive variations, evolutionarily significant units (ESU) across the range will be defined and suggestions for better protection and utilization of the two octopus fishery resources will be advocated.

适应性分化是海洋生物应对环境变化的基本策略，特别是营相对固居生活的底栖生物，但海洋生物响应环境变化的适应性进化潜力却往往被忽略。本项目拟采用基于线粒体和RAD简化基因组测序的现代种群基因组学方法，对相对固居且种群呈深度分化的两种底栖蛸类—长蛸和短蛸的种群基因组核苷酸多态性进行扫描，整合形态学数据，综合探讨两种蛸种群基因组分化模式和地理格局，验证亚种分化是否成立；结合种群历史动态，利用种群遗传学及多变量生态模型评估多重地理与环境尺度对种群分化的影响，解析地理历史事件对谱系格局形成的驱动，揭示生态因子对种群进化的作用，明确关键环境驱动因子；通过中性与outlier位点甄别，鉴定全基因组中可能受环境压力选择的基因位点和基因组区域，解析适应性变异的空间分布及驱动因子，揭示适应性和中性等多重进化力量对谱系分化的影响及相对贡献。两种变异位点相结合，确定显著进化保护单元，提出合理的两种蛸保护与利用策略.

适应性进化是海洋生物应对环境变化的基本策略，特别是对于生活在易变环境但又营相对固居生活的生物类群而言，适应性进化似乎是其赖以生存的基本特性。然而当前人们对于适应性进化在海洋生物进化中的作用和机制的了解还相对较少。本项目选取营相对固居而生活环境复杂多变的2种底栖蛸科动物为研究对象，采用线粒体基因组和RAD简化基因组测序等现代种群基因组学方法，结合形态学指标，研究两种蛸科动物种群基因组分化模式和地理格局，全面解析中性进化和适应性进化在两种蛸种群分化中的作用及形成机制,为全面揭示中国沿海海洋生物种群地理格局形成的过程和一般规律奠定基础。研究结果表明：中国沿海的长蛸和短蛸群体均存在着显著的遗传分化。短蛸群体存在黄、渤海与东、南海南北两大类群的分化，两者以长江口为界，而长蛸群体存在三个类群的分化，其中东山与温州及温州以北的海域都存在显著的遗传分化，上述群体的分化以台湾海峡为界。更新世冰期等古地质历史事件和现今生态隔离（长江口冲淡水）可能是两种蛸种群分化格局形成的主要原因。但冰期过后，两物种各分化类群间在相邻区域通过二次接触而均形成了杂交带，进一步证实了古地质历史对2种蛸种群分化的塑造作用。适应性进化检测未在线粒体基因组中检测到受自然选择的位点，而基因组RAD简化基因组研究结果表明，适应性进化可能在两种蛸种群地理格局形成中也扮演着重要角色，2种蛸的基因组中均有若干渗透调节及免疫相关基因受到了自然选择，推测中国沿海南北大尺度盐度、病原分布等环境因子差异选择压力下，已造成两种蛸的本地适应性进化。本研究首次揭示了中性进化与适应性进化共同作用在2种蛸科动物地理分化格局形成中的作用，为更好的认知环境选择压力下适应性进化的形成规律和作用机制，为2种底栖蛸科动物渔业资源的科学管理与有效保护奠定基础。