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 in southeastern Asia. Its populations are restricted to riparian habitats. The discontinuous distribution might result in high genetic diversification among plants of different river systems. In the present study, leaf samples were collected from populations along six river systems in western Taiwan and the genetic variation was investigated by employing RAPD markers. A total of 255 samples from 17 sampling sites was studied. Eighty random 10-mer primers were screened and six of them, which showed better amplification results, were selected to analyse all of the samples. Data of 34 high-intensity and highly reproducible polymorphic fragments were used in statistical analyses. The results of AMOVA analyses indicated that, of the total variation, 46.84% was attributable to differences among river systems, 16.88% to differences among sampling sites within river systems, and 36.28% to differences among individuals within sampling sites. The results of cluster analysis and principal coordinate analysis revealed that sampling sites of each river system formed distinct clusters and the sampling sites of six river systems were clustered into three main groups according to latitudinal 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.