RAPD markers were used to assess the relationships among 6 species of Sonneratia in the National Mangrove Nature Reserve of Dongzhai Harbor in Hainan. By using the 15 effective 10 -oligonucleotide arbitrary primers, a total of 512 DNA bands were amplified, among which 297 (58.01%) were polymorphic. Based on UPGMA cluster analysis of 512 DNA bands amplified by the thirty primers, a DNA molecular dendrogram was established, which divided 6 species of Sonneratia into three main groups. Group A included 4 species: Sonneratia apetala , S. hainanensis, S. abla, S. ovata, and Group B: S. paracaseolaris and Group C: S. caseolaris only contained one species respectively. Group A could be divided into two subgroups, A1; Sonneratia apetala , S. hainanensis, S. covata and A2: S. abla; Two populations of Sonneratia apetala, which were from Hainan and Fujian (introduced from Hainan) respectively, were compared by RAPDs. The phenotypic frequencies detected by the 15 primers were calculated and used to estimate diversity (H) within sub-populations. Fujian sub-population exhibited 0.669 and Hainan exhibited 0.671 variability. Shannon’s index of phenotypic diversity was then used to partition the diversity within and between sub-populations components. An assessment of the proportion of diversity present within sub-populations, Hpop/Hsp = 0.933, compared with that between sub-populations, (Hsp- Hpop) /Hsp = 0.067, indicates that, on average, most of the diversity (93.3%) is detected within sub-populations; while only 6.7% between populations. The plant introduction of S. hainanensis and S. ovata, which have the nearer genetic distance with Sonneratia apetala , is also discussed.
