Genetic and geographic variation of the mangrove tree <i>Bruguiera</i> in Sri Lanka

The variation in two Bruguiera species in populations from different climatic and macrogeographic regions along the western to southeastern coastal area in Sri Lanka was studied using RAPD (Random Amplified Polymorphic DNA), Intra- and interspecific variation was observed using 20 primers of the 45 primers screened. Some primers showed diagnostic banding patterns and allowed unambiguous differentiation between B. sexangula and B. gymnorhiza without any indication of hybrid individuals. RAPD markers were also used to produce a similarity matrix among individuals of a species. A higher degree of polymorphism was observed within populations of B. gymnorhiza in Rekawa, situated in the climatically intermediate (between the wet and dry) zone, than within populations from the wet zone (Galle and Negombo). RAPD data analysis did not reveal a clear relationship between genetic differences and macrogeographical variation along the western and southern coastal area in Sri Lanka, but indicated that a small population of B. sexangula was genetically different. A more pronounced genetic difference at the population level in B. sexangula than in B. gymnorhiza is suggested

Genetic differentiation between <i>Bruguiera gymnorhiza</i> and <i>B. sexangula</i> in Sri Lanka

The identification of populations of Bruguiera sexangula, Bruguiera gymnorhiza and their putative hybrids in the field is difficult using only morphological and phenological characters. Using a PCR based technique, RAPD (Random Amplified Polymorphic DNA), the genetic variation of Bruguiera populations was studied from contrasting climatic and geographic regions along the southwest coastal region of Sri Lanka. Out of 45 primers screened, 20 primers allowed us to observe polymorphism, not only between species (interspecific) but also within the species (intraspecific). Analysis of RAPD data appears to be helpful in determining the genetic relationship among populations of B. gymnorhiza and B. sexangula. RAPD markers revealed that the two species are well separated without any hybrid position between the two taxa though they occur in mixed stands. Although sampling sizes of populations of this study were small, genetic variation among B. gymnorhiza and B. sexangula populations could be observed. For B. sexangula, it was possible to differentiate each of the three populations, even when using a small number of primers