Abstract: Inter-simple sequence repeat (ISSR) markers were used to analyze genetic diversity and differentiation in eight populations of invasive plant species Eupatorium catarium Veldkamp distributed in Guangdong and Hainan in Southern China. Ten ISSR primers used in this study produced 98 loci, of which 9.8 were polymorphic. At the species level, the percentage of polymorphic loci (P) was 100%, Shannon’s information index (I) 0.4440 and Nei’s gene diversity (h) 0.2916, indicating high genetic diversity in E. catarium. Based on Nei’s G_st value, 72.39% of genetic variance was among individuals within population, 27.61% among populations. Gene flow among populations was 1.3107. Average genetic similarity of the eight populations was 0.8828, while average genetic distance was 0.1257. Unweighted pair group method with arithmetic mean (UPGMA) analysis separated the eight populations into three groups. The six populations of Haikou, Danzhou, Qiongzhong, Sanya, Heshan and Yangjiang were clustered into one group, and Qionghai and Xuwen populations were clustered into two independent groups, respectively. The Mantel test suggested that there was no significant correlation between the genetic distance and geographic distance of the eight E. catarium populations, thus it was likely that the spread of the invasive species in the studied regions was mainly attributed to the events of humanmediated longdistance dispersals of seeds or propagules.

Key words: cadmium, metabolite., sewage, combined stress, maize seedling