The Sea-Floating Plants Floristic Relationship and Genetic Variation between the Nearby Islets and Taiwan（1/3）

Taiwan located under the Pacific warm current, faces Fujian across the Taiwan Strait in its south-west, the Philippines across the Bashi Channel southward, and Ryukyu islands north-eastward. Therefore, the floristic structure in Taiwan not only closely related with those in the neighboring areas, but also is affected by the tropical maritime floristic. The genetic variation of the plants dispersed by sea in Taiwan inferred from ISSR Markers. In this study, the genetic variation and population structure of 68 individuals sampled from 6 wetlands of Avicennia marina were studied using ISSR markers. A total of 8 primers were used and 44 polymorphic bands were obtained. Analysis of molecular variance (AMOVA) revealed that the variance component between population groups was 9.89% ( p< 0.001), among population within groups was 23.22% ( p＜0.001), and among individuals within population was 66.89% ( p＜0.001). The result indicated that there was a significant genetic differentiation existed among varieties. POPGENE analysis revealed that the total gene diversity（H）of Avicennia marina were 0.2492. The population genetic index （Gst） was 0.3339 , while the gene flow index （Nm）was 0.9974, and that indicated the gene flow among population was relatively restricted. The results shown that, the genetic differentiation was high among its populations in Taiwan. Their populations of Avicennia marina was established by few individuals （founders）and grown rapidly in Taiwan, resulting in population differentiation via genetic drift. Since viviparous embryo of Avicennia marina was known dispersed by sea, the formation of high differentiation between the northern and the southern populations should be attributed to the isolation caused by the characteristic of coastal area sea currents that lack of interflows in summer.