Genetic diversity of mangrove plant Sonneratia caseolaris in Hainan Island based on ISSR analysis
海南岛红树植物海桑遗传多样性的ISSR分析

Sonneratia caseolaris is a mangrove species belonging to Sonneratiaceae. The natural distribution in China restricted to Hainan Island. Sample leaves were collected from individuals of three natural S. caseolaris populations of Wanning (WN), Qionghai (QH) and Hengshan (HS) and one population at Dongzhai Harbor (DZG) introduced from nearby area. A total of eighty-six individuals were sampled. Eleven ISSR primers gave rise to 239 discernible DNA fragments of which 194 (81.17%) were polymorphic. The percentage of polymorphic bands at the population level ranged from 40.59% to 50.21%, with average of 45.71%. The Nei's genetic and Shannon's information index were 0.2103 and 0.3256 respectively at the species level, 0.1468 and 0.2210 respectively at the population level. Based on Nei's Gst value and analysis of molecular variance (AMOVA), it showed that higher genetic differentiation had occurred among populations. The genetic identity between populations was 0.9011 on average. Gene flow (Nm) was 0.5787. UPGMA cluster analysis based on Nei's genetic distance divided the populations into two main groups: WN and QH formed one group, while HS and DZG formed the other group. The Mantel test showed that genetic distance was positively correlated with geographical distance, but not significant. The correlation analysis showed that there was no significant relation between population genetic diversity level and environmental factors. Since the genetic diversity of DZG was obviously lower than that of natural populations, the effort of in situ and ex situ protection to QH and WN should be strengthened to conserve genetic diversity.