摘要：
岛屿是开展生物区系与生物地理学研究的天然实验室.海南岛是中国唯一的热带大陆性岛屿,地处中国喜马拉雅植物亚区和马来西亚亚区交界地带,物种来源与迁移历史十分复杂.本文首先分析了海南岛苦苣苔科物种多样性与地理分布格局,然后利用核基因ITS1/2和叶绿体基因trnL-F序列建立海南岛苦苣苔科植物的系统发育树,揭示其物种迁移历史与特有类群的形成时间.海南岛苦苣苔科野生类群虽然仅有14属24种,但包括了扁蒴苣苔属(Cathayanthe)和盾叶苣苔属(Metapetrocosme)2个特有属、8个特有种(含1变种).面积归一化处理后,海南岛该科的特有种比例仅次于广西,远高于云南和邻国越南.物种组成相似度分析结果显示,海南岛与广东省的共有物种最多,这可能是第三纪末期(～3 Ma)几度海进海退过程中,海南岛通过雷州半岛与广东多次连接的结果.海南岛苦苣苔科植物在海拔400-1,000m和1,400m以上形成2个集中分布区,特有种则集中分布在高海拔区域,表明海南岛中南部连绵的高山是苦苣苔科特有种形成与维持的一个重要原因.海南岛有着亚洲苦苣苔科的多个基部类群,且都与东南亚共享;海南岛-中国大陆分布的类群则处于系统树的较新分支,表明海南岛苦苣苔科植物早期是从东南亚迁入.海南岛两个特有属的形成时间约在12 Ma,特有种也都在15-5 Ma才分化出来,这可能与印度板块撞击亚欧板块导致的东亚季风气候(约28 Ma)和此时海南岛远距大陆约100km造成的隔离作用有关.%Hainan Island offers an excellent opportunity to study biodiversity and biogeography as it is the biggest tropical island in China while its flora evolution and biogeographic patterns have remained largely unexplored.Gesneriaceae is a typical tropical plant family,showing diversification centers in southwestern China and the Malay Archipelago.Hainan Island is located between these two ‘hotspots’.In this study,area-adjusted species density and endemic indices of Gesneriaceae on Hainan Island were compared with nearby regions including Guangdong,Guangxi,Yunnan,Guizhou,and Vietnam.The detailed distribution patterns of Gesneriaceae on Hainan Island were also explored by comparing species diversity and endemic proportions among different mountains and altitudes.We also used nuclear ITS1/2 and chloroplast trnL-F sequences to construct a phylogenetic tree of Gesneriaceae on Hainan Island to study dispersal histories and the speciation time of Hainan-endemic species.Our results showed that,although Hainan Island has only 24 Gesneriaceae species,of which eight species and two genera are endemic,it also was characterized by a very high area-adjusted species diversity and endemic index due to its small geographical area.Hainan Gesneriaceae were distributed mainly in high mountainous regions such as Mt.Wuzhi,Mt.Jianfeng,and Mt.Yingge and showed the highest species diversity at both 400-1,000 m and ＞1,400 m a.s.1.The molecular data showed that two endemic monotypic genera,i.e.Metapetrocosme and Cathayanthe,evolved at about 12 Ma,which may have been triggered by the monsoon climate (formed at about 28 Ma).Hainan contains the most basal taxa of Asian Gesneriaceae and shared these with Southeast Asia,suggesting Hainan Gesneriaceae largely originated from Southeast Asia,instead of the Chinese mainland.However,the great similarity of species composition between Hainan Island and the geographically-closest province,i.e.Guangdong,proves that Hainan flora experienced frequent species exchanges with the Chinese mainland recently,likely during the late Tertiary (～3 Ma) when the island was connected with the Chinese mainland.
