COMPARATIVE GENETIC DIVERSITY STUDIES OF SHOREA LEPROSULA (DIPTEROCARPACEAE) USING RAPD AND ALLOZYME MARKERS

Genetic diversity parameters of seven populations oí 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 consistendy lower. This may suggest that RAPD alíele frequencies corrected for HWE deviation may be underestimated. RAPD markers highlighted a larger amount of overall population differentiation (GST) than allozyme. However, GST derived from RAPD genotypic method was not significantly different from GST 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 GST, 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 and 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. Parameter kepelbagaian genetik dianggar ke atas tujuh populasi Shorea leprosula dan Semenanjung Malaysia berdasarkan 50 serpihan RAPD/lokus RAPD putatif dengan dua pendekatan iaitu kaedah fenotip menggunakan indeks kepelbagaian Shannon dan kaedah genotip menggunakan frekuensi alel nul yang dibetulkan untuk penyisihannya daripada keseimbangan Hardy-Weinberg (HWE). Perbandingan dengan keputusan kajian alozim terdahulu menggunakan set individu dan populasi yang sama menunjukkan RAPD genotip menghasilkan peratusan lokus polimorfik dan keheterozigotan jangkaan yang lebih rendah. Ini mencadangkan frekuensi alel nul yang dibetulkan daripada penyisihan HWE mungkin kurang dijangka. Penanda RAPD memperlihatkan tahap perbezaan populasi (GST) yang lebih tinggi daripada alozim. B