Analysis of genetic variation within and among Ulva pertusa (Ulvaceae, Chlorophyta) populations using ISSR markers

Ulva pertusa is a native species to Asia along the western coast of Pacific Ocean, with new occurrence records in the eastern coast of Pacific, the northwest coast of Atlantic and the Mediterranean Sea. However, little is known about its population genetic structure. In this study, twelve U. pertusa populations from 3 coastal areas of China: Qingdao, Yantai and Dalian, were applied to ISSR analysis. The selected 4 ISSR primers amplified 120 polymorphic bands totally. Nei's gene diversity (H) ranged from 0.0729 to 0.1496, and Shannon's information index (I) ranged from 0.1072 to 0.2196. Genetic diversity was greater within Qingdao populations (H = 0.2069, I = 0.3232). Analysis of molecular variance (AMOVA) showed the greatest variance within populations (68.57%), much less variance among populations (22.63%) and among areas (8.79%). Unweighted pair-group mean analysis (UPGMA) indicated that clustering of U. pertusa individuals mainly relates to their populations and geographic distances separating those populations. Genetic differentiation and limited gene flow among U. pertusa populations were indicated by ISSR analysis.