RELATIONSHIP BETWEEN POPULATION GENETIC-STRUCTURE AND RIPARIAN HABITAT AS REVEALED BY RAPD ANALYSIS OF THE RHEOPHYTE ACORUS-GRAMINEUS SOLAND. (ARACEAE) IN TAIWAN

Acorus gramineus Soland. (Araceae) is a rheophyte and is distributed i n southeastern Asia. Its populations are restricted to riparian habita ts. The discontinuous distribution might result in high genetic divers ification among plants of different river systems. In the present stud y, leaf samples were collected from populations along six river system s in western Taiwan and the genetic variation was investigated by empl oying RAPD markers. A total of 255 samples from 17 sampling sites was studied. Eighty random 10-mer primers were screened and six of them, w hich showed better amplification results, were selected to analyse all of the samples. Data of 34 high-intensity and highly reproducible pol ymorphic fragments were used in statistical analyses. The results of A MOVA analyses indicated that, of the total variation, 46.84% was attri butable to differences among river systems, 16.88% to differences amon g sampling sites within river systems, and 36.28% to differences among individuals within sampling sites. The results of cluster analysis an d principal coordinate analysis revealed that sampling sites of each r iver system formed distinct clusters and the sampling sites of six riv er systems were clustered into three main groups according to latitudi nal relationships. The results of the present study indicated that the population genetic structure of the plants of different river systems is highly diversified, which seems to imply that the gene flow among them is very limited.