麻栎遗传变异与分子亲缘地理学研究

Phylogeography is a young, vigorous and integrative field of study that uses genetic data to understand the history of populations. With a lagre distribution area, Quercus acutissima is an important component of deciduous broad-leaved forest and afforestation tree species. However, few studies on the phylogeography of Quercus species have been documented in China. In this study, we determine the sampling strategy according to differences in climate and topography, and conduct studies on the sequence and microsatellite analysis of both nuclear DNA and chloroplast DNA. The research content is divided into three parts. Firstly, based on 10 loci of nSSR and 10 loci of cpSSR data, through analysis of genetic diversity, population structure, and molecular variance, we reveal the level of genetic diversity and population structure on the scale of geographic groups and populations of Quercus acutissima. Secondly, based on the sequence data of 5 cpDNA fragments and 2 nDNA fragments, through analysis of haplotype distribution, phylogeographical patterns, population expansion time, we explain the features of genetic variation of Quercus acutissima and the effect of Pleistocene climate on its genetic structure. Thirdly, based on the data of 10 loci of nuclear microsatellite and 3 cpDNA sequences, through the analysis of Bayesian clustering, F-statistics, testing of isolation migration model, we clarify the relationship and differentiation time of four species of oaks (Quercus). This study has important theoretical and practical significance for understanding of the genetic variation and phylogeographical patterns of Quercus acutissima, and for protection and utilization of germplasm resources.

作为一门年轻有活力的学科，亲缘地理学的使命是采用遗传数据来认识群体历史。麻栎地理分布辽阔，是落叶阔叶林重要组成成分和重要造林树种。然而我国有关栎树亲缘地理学的研究鲜见报道。本项目根据气候和地形差异来决定采样策略，开展cpDNA和nDNA序列分析和SSR分析，研究内容有：①获得10位点nSSR和10位点cpSSR数据，进行遗传多样性、群体结构和分子方差分析，在地理组和群体尺度上揭示麻栎多样性水平及群体遗传结构。②获得的5个cpDNA片段和2个nDNA片段序列数据，分析单倍型分布、亲缘地理模式和群体扩张时间等内容，阐明麻栎遗传变异规律及更新世气候对其遗传结构的影响。③获得10位点nSSR和3个cpDNA片段序列数据，通过贝叶斯聚类、F-统计、隔离迁移模型等分析，阐明麻栎组四种栎树的亲缘关系和分化时间。本研究对于认识麻栎遗传变异规律和亲缘地理模式，以及种质资源保护与利用具有重要的理论和实践意义。

本项目以我国落叶阔叶林重要组成成分和重要造林树种麻栎为主要研究对象，开展遗传变异与亲缘地理学研究。主要研究工作包括：①获得30个麻栎居群707个个体的12个nSSR位点数据。②获得30个麻栎居群401个个体的3个cpDNA片段序列数据。③获得小叶栎17个居群159个个体的5个cpDNA片段序列数据。主要进展包括：①鉴定了麻栎19种叶绿体单倍型，揭示了其地理分布规律与遗传多样水平。②支持麻栎天然居群在更新世冰期内具有复合避难所，中国中部可能是麻栎谱系在间冰期扩张并融合的“熔炉”，具有更高的遗传多样性水平。③近似贝叶斯计算分析结果表明，麻栎和小叶栎分化时间为16.7 Ma，小叶栎和栓皮栎的分化时间为6.37 Ma。④采用Bioclim模型、Domain模型和Maxent模型预测了麻栎、栓皮栎和小叶栎的潜在地理分布区；采用流式细胞术测定了麻栎(1.87 pg)和栓皮栎(1.92 pg)的基因组大小。研究结果深化了对栎属遗传变异规律和亲缘地理模式的认识，对于麻栎种质资源保护与利用具有重要的理论和实践意义。