金虎尾科“花保守性”在亚洲的适应转变与进化后果——以亚洲特有属风筝果属的镜像花为例

Malpighiaceae is well-known for the ‘Malpighiaceae route’, which is a classic model to explain inter-continent disjunctions and long-distance dispersal of tropical plants. This family has about 1300 species, most of which are endemic to the New World and are characterized by ‘floral conservatism’. Floral conservatism in the neotropical Malpighiaceae refers to its stereotyped bisexual flowers and clawed petals, with paired oil-glands on each sepal, a result from co-evolution with oil-collecting bees. ..The Asia-endemic genus Hiptage, however,has a highly-specialized pollination system, i.e. mirror-image flowers, together with other striking floral traits such as extremely-reflexed petals and single nectar-secreting gland. These unusual floral syndromes indicate a special case of evolutionary transition of ‘floral conservatism’ in Asia, providing an excellent opportunity to examine ecological and evolutionary consequences of pollinator shifts during inter-continent dispersal, not only for Malpighiaceae but also the other plants with a dispersal pattern like ‘Malpighiaceae route’. ..To examine the evolutionary transition of ‘floral conservatism’ and its effects on speciation in Hiptage, three species, H. benghalensis (1 big calyx gland; widespread), H. minor (no calyx gland; endemic to China), and H. tianyangensis (1 small calyx glands; endemic to China), will be studied for their floral syndromes and pollination mechanism. Special attentions will be paid to their possible floral isolation mechanisms associated with mirror-image flowers and the herkogamy (the separation of the stigma and the fertile anther). The geographic isolation caused by river, karst landscape, and tropical monsoon will be also considered...To demonstrate the speciation history and dispersal route of the Hiptage, molecular phylogeny and biogeographic patterns of the widespread and narrow-endemic species in the two diversity and endemism centres of Hiptage (the boundary areas between Guangxi, Guizhou and Yunnan provinces in China and the northern mountains in Thailand) will be studied using both nuclear and chloroplast DNA sequences. The results will be also helpful to understand the formation and evolution of the globally-important biodiversity hotspots in these regions. The information of floral evolution and pollination shift in Hiptage will add much-needed information on Asian taxa of Malpighiaceae for the study of complete evolution history of the ‘Malpighiaceae route’. ..To explore the evolutionary adaptations associated with ‘Maplpighiaceae route’ from a global context, pollination systems and floral syndromes of Hiptage, other Asian genera and all American and African genera will be mapped on an complete and up-date phylogeny of Malpighiaceae. The patterns of floral evolution and pollination shifts of ‘Malpighiaceae route’ can be determined based on phylogenetic analysis.

根据金虎尾科植物地理分布格局与迁移历史提出来的“金虎尾路线”，是解释植物洲际间断分布与长距离扩散的经典模式。金虎尾科在起源中心热带美洲约有1100种，但花部特征非常保守；而亚洲特有的风筝果属（Hiptage）出现了镜像花、反折花瓣、分泌糖分的萼片腺体，可能是金虎尾路线在亚洲发生特化适应的一个典型代表。本申请项目拟（1）对比风筝果属广布种和狭域特有种的花部特征与传粉者类型与体型的相关性，揭示镜像花可能存在的传粉隔离机制及其对物种分化的作用；（2）通过分子系统与生物地理学方法，解析风筝果属物种分化历史与迁移格局及在中国滇黔桂交界区形成特有中心的原因与过程；（3）利用系统发育方法，在属水平上重建金虎尾路线全球扩散过程的传粉转变与花进化历史。本项目以风筝果属为例阐明了亚洲金虎尾科植物的迁移历史与传粉适应，揭示整条金虎尾路线的适应进化过程，有助于深入理解植物洲际长距离扩散的繁殖适应与物种进化规律。

以风筝果属的镜像花和物种分化历史为例，研究了亚洲金虎尾科植物的长距离扩散历史与物种适应分化规律，以全面揭示生物地理学经典模式“金虎尾路线”的进化适应过程，提升金虎尾路线对热带植物长距离扩散和物种适应进化研究的指导价值。研究内容主要包括三个方面：（1）风筝果属镜像花及相关花部特征的传粉适应机制、（2）风筝果属物种之间的繁殖隔离机制、（3）风筝果属物种分化和迁移历史、（4）金虎尾路线花进化与传粉转变历史重建。.结果发现：.（1）镜像花主要花部特征雌雄异位在物种间和物种内存在较大的变异程度，不同程度的雌雄异位对应着不同体型大小的传粉昆虫。因此，镜像花通过雌雄异位程度的变化，适应了不同地区里的传粉昆虫，导致传粉隔离和物种分化。这种现象既存在于不同物种之间，也存在于广布种风筝果（Hiptage benghalensis） 的不同地理种群之间。这些结果证实了镜像花可能通过雌雄异位的变化导致了传粉隔离，促进了风筝果属的物种分化。.（2） 结合核基因 ITS 片段、简化基因组测序技术(RAD-seq)等手段，对采集到的 25 个物种建立了目前为止风筝果属最全的分子系统树，较好地解析了风筝果属物种分化历史与扩散路线，提出越南南部可能是风筝果属的起源中心，随后向北沿着澜沧江、怒江和红河等河谷扩散到我国云南和广西，并向南沿着马来半岛扩散到东南亚和菲律宾；同时还探讨了主要花部特征如花瓣反折、花瓣颜色、花萼腺体以及翅果类型的进化历史。.（3）发现并公开报道了2个新种：弯翅风筝果、泸水风筝果。这两个种都位于我国云南西北部山地。据此提出了中国西南部山区不仅是物种分布中心，还是亚洲热带植物物种快速辐射形成的“进化前沿”，提出季风气候、西南地区破碎地形地貌以及风筝果属特殊的镜像花等是导致风筝果属在这一带快速物种分化的主要因素。..科学意义：风筝果属是金虎尾科在亚洲的物种多样性最高的亚洲特有属，也是生物地理学经典模式“金虎尾路线”洲际长距离扩散的最后一步，但过去的相关研究仅关注了南美和非洲，基本完全没有亚洲类群的研究。本项目补充了“金虎尾路线”的亚洲部分，使得整个金虎尾路线得以完整解析，对提高这一生物地理学经典研究模式的指导意义具有积极作用，同时对对认识亚洲热带植物迁移和我国热带植物成分的组成与形成历史具有重要意义。