Gentic diversity of a tropical tree species, shorea leprosula miq.(dipterocarpaceae), in malaysia: lmplications for conservation of genetic resouces and tree improvement

摘要

Genetic diversity and population genetic structure of Shorea leprosula was investigated using seven natural populations distrbuted throughout Peninsular Malaysia and one nartural population from Bornco. The mean population and speccies level geneticdiversity were exceptionally high (H_e =0.369 +-0.025 and 0.406+-0.070, respectively). Heterozygosity varied among populations, ranging from 0.326 to 0.400, with the highest values found in the populations from central peninsular Malaysia. Correlationsamong ecological factors (longitude, latitude, and annual rainfall) were not significant (p > 0.05), indicating that these ecological variables were not responsible for the observed genetic differences among populations. The Bangi adult population exhibited a higher level of observed heterozygosity but lower fixation indices in comparison to its seedling population. All other seedling populations also showed positive fixation indices (F), indicating a general excess of population homozygotes. This alsomay suggest selection against homozygotes between the seedling and abult stages. A low level of population differentiation was detected (G_(ST)=0.117 with the Lambir population andG_(ST)=0.085 without the lambir population). Furthermore, gene flow (N_m)between populations was not significantly correlated with geographical distances for the populations within peninsular Malaysia. Cluster analysis also did not reflect geographical proximity and gave little insight into the genetic relatedness of the populations, This may indicate that the populations sampled are part of a continulous population with fragmentation having occurred in the recent past.