论中国海南岛的生物地理起源

On the biogeographical origin of Hainan Island in China

当前海南岛植物区系以热带分布的科和属占绝对优势,在属的地理成分上热带亚洲分布属的比例最高,显示出它是一个热带性质的植物区系,并具有热带亚洲亲缘。在海南植物区系中,仅有7个特有属和约10%的特有种,极低的特有性显示了它具有明显的大陆起源特征。通过比较研究发现,中国海南植物区系与越南植物区系关系最密切,其次是广西植物区系。在哺乳动物上,也显示出与植物区系类似的生物地理格局,中国海南与越南的联系最密切。古植物学研究揭示海南岛在始新世时曾具有亚热带性质的植物区系和亚热带气候,处在比现今更北的位置。古地磁学研究揭示在中生代时期海南岛连接着越南和中国广西,处于比现在高5~6个纬度的位置。综合各方面的研究,我们从生物地理的角度提出中国海南岛在始新世时曾连接着越南和中国广西,后来发生了向东南移动和旋转,最终到达现在的位置。

Based on biogeographic study of Hainan Island in China,only seven endemic genera and 397 endemic species of flora have been identified(accounting for^10%of total flora),indicating that Hainan has a very low number of endemics and a disharmonic flora.Furthermore,the extremely low endemism is indicative of a continental origin.Although Hainan is closest to Guangdong(~20 km),it has more floristic similarities to Vietnam and Guangxi(China)at the family and genus levels.Of note,only 3.7%of Hainan genera show East Asian distributions.Furthermore,Hainan mammals show a biogeographic pattern similar to that of flora,with the highest proportion of mammals sharing with Vietnam and the lowest proportion sharing with Guangdong.Thus,the disharmonic flora and fauna of Hainan Island suggests that its present location is not its original site,and that the island may have been in contact with northern Vietnam and Guangxi in southwest China.Palaeobotanical studies suggest that Hainan Island may have been in a much more northerly location with a subtropical climate during the Eocene.This supports the deduction that Hainan was,at some point,adjacent to Vietnam and Guangxi.The current results are concordant with palaeomagnetic and volcanism studies,which suggest that the Qiongzhou strait formed by an active rift structure,and Hainan drifted to its present location by moving southeast from higher latitude.The opinion espoused in this paper on the biogeographical origin of Hainan Island has support from other studies on endemic mammals(Hainan gymnure,Mammalia,Lipotyphla),insect genera(Hesperiidae:Pyrginae:Tagiadini),Stedocys spitting spiders,earthworms(Megascolecidae),and other plant taxa.