Molecular phylogeny of mangroves VI. Intraspecific genetic variation in mangrove species Excoecaria agallocha L. (Euphorbiaceae)

Genomic DNA from 84 individuals of Excoecaria agallocha from seven mangrove populations were analysed for random amplified polymorphic DNAs (RAPDs) us ing 16 random 10-mer primers. Polymorphism within populations varied from 2 0% to 31%. At the interpopulation level, 111/149 (74%) of RAPDs were polymo rphic. Restriction fragment length polymorphism (RFLP) analysis of 21 indiv iduals (3 individuals randomly selected from the 7 populations) using 30 pr obe-enzyme combinations revealed a high level of interpopulation polymorphi sm (62.2%) indicating interpopulation genetic divergence. The polymorphic R APDs and RFLPs were pooled, and clustering was carried out based on mean si milarity for individual populations. The dendrogram showed groupings of pop ulations from the West and East Coasts of India into separate clusters, at 60% similarity level. Further, RAPD and RFLP analysis of male and female pl ants showed approximately the same level of variation in both sexes, and no sex-linked markers were found. These results demonstrate that considerable intrapopulation and interpopulation genetic variations exist in E. agalloc ha, and that lack of genetic variation is not the reason for the morphologi cal uniformity observed across the range of the species.