COMPARATIVE GENETIC DIVERSITY STUDIES OF <em>SHOREA</em> <em>LEPROSULA</em> (DIPTEROCARPACEAE) USING RAPD AND ALLOZYME MARKERS

Abstract

Genetic diversity parameters of seven populations of Shorea leprosula from Peninsular Malaysia were estimated based on 50 RAPD fragments/putative RAPD loci using two approaches, i.e. phenotypic method using Shannon's index of diversity and genotypic method with null-allele frequency corrected for deviation from Hardy-Weinberg equilibrium (HWE). Comparison with previous allozyme results based on the same set of individuals and populations showed that the percentage of polymorphic loci and expected heterozygosity derived from RAPD genotypic method were consistently lower. This may suggest that RAPD allele frequen cies corrected for HWE deviation may be underestimated. RAPD markers highlighted a larger amount of overall population differentiation (G_sr) than allozyme. However G_sr derived from RAPD genotypic method was not significantly different from G_sr. based on allozyme (p = 0.372). It is argued that genetic diversity parameters derived from RAPD genotypic method can be underestimated but might still able to provide a reliable estimate of G_sr if the bias affects proportionally both the genetic diversity within population and total genetic diversity. No significant correlation between similarity matrices based on RAPD and allozyme may indicate that these marker types give different estimates of genetic relationship among the populations tested. However, the correlation found between dendograms constructed on RAPD genotypic arid allozyme similarities was fairly high (r = 0.839, p = 0.01). In fact, RAPD genotypic method resulted in a more definitive separation of populations than allozyme. The greater discriminatory power of RAPD compared to allozyme may be due to its greater coverage of the genome.