Molecular phylogeny of mangroves II. Intra -and inter-specific variation in Avicennia revealed by RAPD and RFLP markers

Abstract

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 officinalis (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. officinalis (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.