中国西南地区半叶趾虎属天空岛屿物种的分子系统地理学

The Hemiphyllodactylus species of China are mainly distributed in mountainous areas with elevation from 1000 to 2400 meters. Most of them are separated into small populations, isolated by low-elevation habitats from each other. Moreover, these species are restricted in distribution and have high endemism. All these characters are concordant with the pattern of so called sky islands. Ecological adaptation, restricted gene flow and genetic drift in small populations may contribute greatly to the species diversity of this genus. As a result, undescribed species of Hemiphyllodactylus might be discovered in isolated populations. Moreover, the sympatric distribution of mitochondrial haplotypes from two species suggests vertical migration and gene flow responding to the glacial climate changes, which is another character of sky islands. In this project we will discuss speciation and genetic diversity of sky island species of Hemiphyllodactylus in Southwest China; we will discover genetic divergent lineages by using phylogenetic and distance analyses, and compare the pattern of molecular evolution between lineages; we will examine the population expansion and compression during the glacial climate changes and the existence of interspecific gene flow; and we will finally discuss the impact of interspecific hybridization on species diversity and their evolutionary trajectories. These results will be significant for disclosing the processes of population divergence, ecological adaptation, speciation, secondary contact and introgressive hybridization.

半叶趾虎属物种在中国大陆的分布符合天空岛屿的分布模式，如生活在海拔1000-2400米的高原山区；多为间断分布的小种群；各岛屿种群之间相互隔离；物种局域分布且特有性高。生态适应、受限的基因流以及遗传漂变等均可能会增加该属的物种多样性。因此，在隔离的种群中很可能还存在尚未描述的半叶趾虎属物种。此外，物种对之间线粒体单元型的同域分布，提示可能存在天空岛屿的另一特点——与冰期-间冰期气候回旋相关的分布区垂直移动与基因流。本项目拟探讨中国西南地区半叶趾虎属天空岛屿物种遗传多样性的形成机制；通过系统发生和距离分析发现存在遗传分歧的支系，并比较支系间的分子进化模式；通过种群动态分析，检测是否存在伴随气候变化的种群收缩和扩张，以及种间基因流；探讨种间杂交对物种多样性和进化轨迹的影响。这些研究结果对于揭示种群歧异、生态适应、物种形成、二次接触及渐渗杂交过程具有重要意义。

半叶趾虎属物种在中国大陆的分布符合天空岛屿模式，故而有较高的物种多样性和特有性。线粒体ND2基因序列分析显示，采自广东大成的半叶趾虎标本与新描述的都庞岭半叶趾虎关系最近，但仍有3.8%的遗传距离，提示种内分歧甚至隐存种的存在。种内分歧还在云南半叶趾虎和昌宁半叶趾虎中发现，提示隔离的分布和有限的基因流促进或驱动了分歧。利用RAD-Seq技术从云南半叶趾虎中筛选出了20对多态性较高的微卫星标记，并用于该属的种群结构研究。结合国外所有半叶趾虎序列的系统发生分析结果显示，中国产物种并未聚在同一个分支内：位于中国分布区最西南边缘的龙陵半叶趾虎、昌宁半叶趾虎和金平半叶趾虎与分布于缅甸的多个物种聚为一支，而其余的五个物种与分布于越南的多个物种聚在同一分支，提示两条独立的物种扩散路径。种群动态分析支持云南半叶趾虎、金平半叶趾虎、龙陵半叶趾虎和昌宁半叶趾虎都经历过种群扩张，扩张时间与末次冰期时间大致一致。生态位建模结果显示，在末次盛冰期时半叶趾虎的适生区范围更大，提示冰期气候有利于半叶趾虎的种群扩张。核基因和线粒体基因数据都支持云南半叶趾虎与金平半叶趾虎，以及龙陵半叶趾虎和昌宁半叶趾虎之间存在二次接触，证实了半叶趾虎在天空岛屿分布区上的垂直迁移和基因流。