中文摘要：

通过测定来自国内5个分布地点的海南草海桐Scaevola hainanensis Hance群体核核糖体基因间隔区序列（nuclear ribosomal internal transcribed spacer region,ITS）,一方面评估海南草海桐的遗传多样性大小,另一方面,结合Gen Bank中已有的草海桐属物种ITS序列来共同进行分子系统发育分析,旨在确定海南草海桐在草海桐属中的系统位置。研究结果表明海南草海桐遗传多样性水平极低,作为一种珍稀植物在分子水平上同样面临灭绝的风险。而分子聚类结果发现海南草海桐位于Scaevola组里的北半球谱系,并与夏威夷本地物种的亲缘关系最近,两地草海桐属物种之间可能存在祖先—后代（progenitor-derivative）的扩散模式。研究结果同时否定了Scaevola组的单系性以及海南草海桐由同域广布种草海桐演化而来的假说。

英文摘要：

Genetic diversity of Scaevola hainanensis Hance is estimated based on the sequences of nuclear ribosomal internal transcribed spacer region （ITS） from five populations distributed in China. Further, phylogenetic analysis of the S. hainanensis is performed based on combined ITS sequences data with other species of Scaevola and outgroups available from GenBank. The results shows that the genetic diversity of S. hainanensis is very low, implying that it is at risk of extinction at the genetic level as a rare plant. In the phylogenetie tree, S. hainanensis is located in the Northern Hemisphere lineage and closest to the elade consisting of local species in Hawaii with high support value, which imply the progenitor-derivative dispersal pattern of Scaevola species between Asia and Hawaii. The results did not support the monophyly of S. sect Scaevola and the hypothesis that S. hainanensis is derived from a widespread and sympatric species S. taccada is rejected based on the present result.