Random amplified polymorphic DNA (RAPD) and restriction fragment length polymorphism (RFLP) markers were
used to estimate intra- and inter-specific variation in three species of an exclusive mangrove genus, Avicennia. Intrapopulation
polymorphism among the 10 populations of Avicennia marina, as measured by percentage of polymorphic RAPDs, varied
between 17.8 and 38.9%, with a standard deviation of 7.28, and the coefficient of variation was 26.5%. Polymorphism in
Avicennia ofJicinalis (Pichavaram population, 32.3%) and Avicennia alba (Coringa population, 37.8%) was greater than the
intrapopulation variation observed in the populations of A. marina from each of the respective locations. It was greater than the
average percentage of polymorphism at the intrapopulation level (27.47%) but far less than the variation measured at the
interpopulation level in A. marina. Interpopulation variation in A. marina (76.7% for RAPDs and 66% for RFLPs) was greater
than the variation in any individual population of this species, indicating a high degree of divergence between the populations.
Interpopulation variation as revealed by RAPD and RFLP markers did not indicate the existence of more than one distinct entity
in this species in India. The implications of these observations in genetic sampling and conservation are discussed. Statistical
analysis of 109 RAPDs and 84 RFLPs observed in one representative genotype from each species showed that the widely
distributed A. marina was more closely related to A. alba (genetic distance (1 - F) = 0.22) than to A. ofJicinalis (genetic distance
(1 - F') = 0.37). RAPD analysis of six randomly selected genotypes in each species and principal component analysis of the data
also favoured this observation.