叶绿体DNA标记在谱系地理学中的应用研究进展

谱系地理学研究旨在探究历史上发生的影响目前遗传谱系系统发育和空间分布格局关系的生态与进化过程。叶绿体DNA具有单亲遗传、低突变率、单倍体等特征, 其分子标记不同程度地保留着植物长期进化的历史遗传痕迹, 有助于深度解析谱系地理变异的形成机制。本文探讨了上述特征是怎样影响分子标记的选择、扩大或缩小群体遗传结构分化、延长或缩短空间基因溯祖时间、促进或阻碍种间基因渐渗及谱系分选(复系、并系和单系形成)进程, 重点阐述了这些影响过程的理论基础, 并结合实际例子阐述谱系地理研究进展。由于位点间在突变率、选择强度及它们与漂变互作等方面存在异质性, 今后一个研究重点就是基于叶绿体全基因组序列分析谱系地理变化格局, 包括分析DNA位点间的基因渐渗或基因流动程度差异分布及沿着叶绿体DNA序列上谱系分选差异分布。

Advancing phylogeography with chloroplast DNA markers

Phylogeography seeks to identify the historical ecological and evolutionary processes underlying modern-day phylogenetic relationships across a spatial gradient. Owing to the characteristics of uniparental inheritance, low mutation rates and haploid, chloroplast DNA (cpDNA) markers record the events occurring in historical long-term evolutionary processes to different extents, and hence aid in understanding the mechanisms for phylogeographic variation. Here we discuss how these characteristics affect cpDNA marker selection, how they increase or reduce population genetic differentiation, how they lengthen or shorten the average gene coalescent times, how they promote or impede gene introgression among species and how the process of lineage sorting functions from polyphyly to paraphyly to monophyly. We reviewed the theoretical bases of these mechanisms, as well as the progress made in empirical studies regarding the theories of phylogeographic variation. Because of the heterogeneity of DNA sites in mutation rate, selection strength and interactions with genetic drift effects, one study to examine the genome-wide pattern of phylogeography will be necessary in the future. This must include the analysis of differential gene introgression and gene flow among sites, as well as the distribution of the differential phases of lineage sorting along the chloroplast genome.