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Genetic variation of Avicennia marina in the costal area of Vietnam was examined using microsatellite and AFLP markers. By using five microsatellite loci a total of 21 alleles were detected. The average number of alleles per locus per population ranged from 1.667 to 3.000. The observed heterozygosity varied from 0.180 to 0.263, with an average of 0.210 indicating relatively low level of genetic variation comparing to the previous studies on A. marina in the worldwide range. The expected heterozygosity was larger than the observed heterozygosity leading to positive inbreeding coefficients in all the six populations. Highly significant departures from Hardy-Weinberg Equilibrium were detected in four populations. AFLP analysis revealed a total of 386 loci, of which 232 (60.1%) were polymorphic. In congruent with microsatellite markers relatively low levels of genetic variation were detected at both gene and nucleotide levels ( H = 0.086; π = 0.0054). Reduced level of genetic variation was found in the central population, and in the southern populations. Both microsatellite and AFLP markers revealed large genetic differentiation ( F ST = 0.262 and 0.338, respectively) indicating strong genetic structure among regional populations.Pairwise genetic distance by AFLP showed two populations in the north and the other two in the south are closely related each other.

Genetic variation of the mangrove genus Kandelia (Rhizophoraceae) in the South China Sea region, in four populations in Vietnam and in one population each in Iriomote, Japan, and Bako, Borneo, was evaluated using microsatellite markers. A total of 54 alleles in the six populations were detected by using four microsatellite loci. The two northern Vietnamese populations (Don Rui and Xuan Thuy) showed a high allelic diversity (40 alleles in total) and a high level of gene diversity (H E = 0.773 on average). In contrast, the two southern Vietnamese populations (Can Gio and Ngoc Hien) showed low allelic diversity (11 alleles in total) and a low level of gene diversity (H E = 0.244 on average). There was only one allele common to the two regions. The Iriomote population was genetically related to the northern Vietnamese populations, while the Bako population was related to the southern populations. The findings and the morphological observations indicate that these two genetically differentiated vicariant lineages represent two different species groups, Kandelia obovata Sheue, Liu, and Yong for northern Vietnam and Japan and Kandelia candel (L.) Druce for southern Vietnam and Borneo. The difference in the amount of genetic variation shows that these two species experienced a different adaptive process during the past glacial ages.

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