喜马拉雅山脉地区象牙参属植物物种形成的历史成因

The Himalayas is one of the global biodiversity hotspots, which locates in the southern margin of the Qinghai-Tibetan Plateau. Although numerous researches have been done to reveal the origin and evolution of organisms on/around the Qinghai-Tibetan Plateau (QTP), the Himalayas is still a forgotten region to comprehensively understand the biological diversification around the QTP. Especially, the in-situ speciation within the Himalayas is poorly known. .There are two speculations on the in-situ speciation within the Himalayas: species diversification driven by the uplift of the QTP, and hybridization and species divergence caused by the Quaternary climate change. Our previous study on biogeography of Roscoea Sm. indicated that Roscoea originated at the Himalayas associated with the uplift of the QTP during the early Oligocene and then formed disjunctive distribution between the Himalayas and the North Indochina Peninsular driven by the uplift of the QTP and the rapid extrusion of Indochina Peninsular around the Oligocene-Miocene boundary. However, in-situ speciation of Himalayan clade of Roscoea is still unknown. According to the allopatric distribution among species along the altitudinal gradients and between different habitats, and the conflict of preliminary phylogenetic tree between nuclear DNA (nrITS) and chloroplast DNA (trnH-psbA, trnL-trnF) of Roscoea, we proposed hypotheses that altitudinal-gradient speciation was driven by the uplift of the QTP and hybridization was derived from the secondary contact between high-elevation species and low-elevation species during the Quaternary ice age, and the speciation of a isolated species (R. brandisii) on the island-like mountains (Shillong Plateau) at northeastern India was also driven by the Quaternary climate change..To test the hypotheses, we intend to integrate the Restriction-site Associated DNA sequencing (RADseq) with the ecological niche modelling (ENM) to reveal the in-situ speciation processes of Roscoea within the Himalayas. First, we will reconstruct the phylogenetic relationships among Roscoea species within the and test speciation scenarios with gene flow and divergence time among species based on coalescent methods using single nucleotide polymorphisms of RADseq. Second, we will simulate the potential habitats among species during current, the Last Glacial Maximum and the Last Interglacial and then calculate the dispersal velocity between two periods within one species using analysis of ENM. Finally, all above results will be correlated with tectonic history of the Himalayas and the Quaternary climate change to recover the processes of allopatric speciation and hybridization of Roscoea within the Himalayas. This research will shed light on the historical drivers of in-situ speciation of Roscoea and new insight of biological diversification within the Himalayas, as well as scientific basis for conservation and effective use of plant resources in this region.

喜马拉雅山脉地区位于青藏高原南缘，是世界生物多样性的热点地区之一，然而，该地区却成为理解青藏高原及其邻近地区生物多样性起源和演化研究中缺失的一环，尤其对该地区内的原地物种形成过程知之甚少。我们前期研究表明姜科中的特殊类群象牙参属起源于喜马拉雅山脉地区并在该地区内分化出了一个特有单系进化分支，分支内的物种形成和分化可能受喜马拉雅山脉抬升和第四纪气候变化的驱动。本项目拟以该单系分支为研究对象，从物种水平开展物种形成和演化机制研究：基于简化基因组测序（RADseq）数据重建种间系统演化关系并检测物种形成模型，确定物种进化顺序和杂交物种形成的驱动力；通过生态位模拟分析第四纪冰期－间冰期气候变化对各物种分布区的影响。以期阐明喜马拉雅山脉地区象牙参属植物的物种形成过程及地理分布格局的历史成因。项目的实施有望为理解喜马拉雅山脉地区生物多样化机制提供新的认识，为该地区植物资源的保护和有效利用提供科学依据。

喜马拉雅山脉是世界生物多样性热点地区之一，对于该地区物种形成过程的认识相对匮乏，阻碍了我们对该地区生物多样性起源与演化的了解。本研究以分布于喜马拉雅山脉的象牙参属植物为材料，利用简化基因组测序得到的高通量分子标记，构建了高支持率的种间进化关系树，利用ABBA–BABA及基于溯祖模型的方法，分层次检测了物种之间的基因渐渗，结合生态位模型模拟，分析了象牙参属植物在该区域的物种分化过程。基因渐渗结果显示当今物种之间并未检测到显著的基因渐渗，而祖先分支与当今物种间存在不对称的基因流。生态位模型模拟的结果显示象牙参物种在温度降低时存在向低海拔迁移的趋势。结合分化时间及喜马拉雅山脉的形成历史，我们提出象牙参属植物的早期分化可能收到喜马拉雅山脉快速隆升的影响，经历了隔离分化过程，而大多数物种的分化是在喜马拉雅山脉快分化之后发生，经历的是迁移分化过程。在本项目的资助下，项目负责人与国内外同行开展了深入的交流与合作，发表SCI论文3篇，中文核心期刊论文1篇，项目负责人的学术水平得到显著提升。