Comparative study of AFLP and microsatellite variation in four Dipterocarp species from natural and artificial populations in Sarawak, Malaysia

Abstract

Degrees of genetic variation accumulated in four dipterocarp species in Lambir Hills National Park, Sarawak, Malaysia were estimated and compared with those in a man-made forest in Bakam Experimental Reserve using microsatellite and AFLP markers. By using 2 to 3 microsatellite loci, 9 to 14 alleles were detected. The average observed heterozygosities for Dryobalanops lanceolata, D. aromatica, Shorea beccariana and S. macrophylla in the natural population were 0.400, 0.400, 0.580 and 0.516, respectively, and expected heterozygosities were 0.603, 0.461, 0.685 and 0.745, respectively. In all of the four species, excess homozygotes were observed. Significant deviation from the Hardy-Weinberg equilibrium was detected in D. lanceolata and S. beccariana. AFLP analysis in the natural population revealed that 94.6 to 99.7% of the fragments were polymorphic. The average heterozygosities for these species were 0.220, 0.232, 0.221 and 0.211, respectively. These values were much larger than those obtained in tree populations such as Japanese beech and Japanese oak populations in temperate deciduous broad leaf forests. Genetic variation in the artificial population was compared with that in the natural population. Both the average expected heterozygosities and the number of alleles in the microsatellite loci were reduced in the artificial population. Some distortions such as linkage disequilibrium and the deviation from the Hardy-Weinberg equilibrium appeared in the artificial population of S. beccariana. The use of seeds collected from a limited number of mother trees to make the experimental site is thought to be the cause of the loss of genetic variation.