利用简化基因组研究麻花艽和管花秦艽的基因流动态历史

It requires a long time from the divergence between two species until it reaches complete reproductive isolations. Interspecific gene flow would rise if population sympatrically distributed during population divergence. The levels and cessation of the interspecific gene flow will oscillate dependent on the size of overlapped distributions and species-specific selection. Climate change is a major component that affects the distribution of species, it also affects the range of overlapped distributions and levels of gene flow. Our previous studies suggested that some populations of Genetiana straminea and G. siphonantha in the Qinghai-Tibet Plateau had experienced interspecific gene flow and introgressions in the history, which resulted in the concerted evolutions of the nuclear ITS copies of one species to those of the other in a few populations. In addition, interspecific F1 hybrids can be detected in the sympatric distributions of two species. In this study, we aim to address the following two questions based on genomic RAD-Seq data: (1) interspecific gene flow oscillated in the past, whether it is correlated with past climatic oscillations; and (2) whether historical gene flow would reinforced or reduced genetic divergence between two species. Our results will provide evidence for understanding how alpine plants diverged in the Qinghai-Tibet Plateau and how speciation process would been affected by climatic changes.

两个物种从开始分化到完全生殖隔离，需要持续较长的时间。在分化过程中，如果物种同域分布，则会发生种间杂交和基因流。其中基因流强度和持续时间与物种分布重叠区大小以及物种特异性自然选择强度密切相关，而气候变化是影响物种分布的重要因素之一，它会影响分布重叠程度和基因流强度。研究发现，青藏高原地区分布的麻花艽和管花秦艽历史上曾经发生过基因流和基因渗入，导致一个物种部分种群的ITS拷贝向另一物种致同进化；并且现今仍在很多同域分布地发生种间杂交，存在许多F1代杂交个体。本项目在此基础上，拟使用简化基因组方法，对两个物种同域和异域分布种群取样，生成群体水平上的基因组数据，用以验证:两个物种的基因流存在一定的波动变化，这种变化是否与过去气候变化具有一定的相关性;历史上的基因流是否会导致物种间遗传分化的加强或减弱。研究结果将为理解青藏高原高山植物的物种分化以及气候变化如何影响物种分化提供一定的理论依据。

物种分化过程中可能会发生种间杂交和基因流, 但是青藏高原地区分布的麻花艽和管花秦艽之间的基因流变化是否和气候变化相关，历史上的基因流是否会导致物种间遗传分化的加强或减弱？这些问题尚待解决。本项目对两个物种同域和异域分布种群进行了取样，获取了群体水平上的转录组数据，数据分析结果表明从麻花艽到管花秦艽存在明显的基因渗入，并验证了两个物种的基因流存在一定的波动变化。这种变化与过去气候变化具有一定相关性，溯祖模型结果显示基因渗入是两个物种分化后，自末次冰盛期以来两个物种之间出现了持续的基因流。基因流的出现导致了物种间遗传分化的减弱。本研究结果为理解青藏高原高山植物的物种分化以及气候变化如何影响物种分化提供一定的理论依据。