Abstract

Afzelia xylocarpa is listed as an endangered species on the IUCN World list of Threatened Trees, due to over exploitation for its valuable timber and habitat loss, have resulted in a rapid decline of populations size and local population extinction. Understanding of the processes that determine population genetic structure, gene flow and mating systems is important to conserve and manage the existing populations for this endangered tree species. This study describes the level of genetic diversity and differentiation of fifteen populations of A. xylocarpa in Thailand. Genetic variations at seven nuclear microsatellite loci were examined. The seven nuclear microsatellite loci employed detected a total of 53 alleles (n=432). The nSSRs data indicate that a high level of genetic diversity (H_S = 0.575) and low level of genetic differentiation among the 15 examined A. xylocarpa populations. The observed level of genetic differentiation among the 15 populations was low, as revealed by F_ST = 0.074 and G_ST = 0.078. The results for the nSSRs suggested that all of the populations in North Eastern, Central Thailand and the Klong Lan populations harbored the high genetic diversity and less divergent from the other populations. Therefore, these populations should be assigned the highest priority for conservation of this species.

Key words: Afzelia xylocarpa, genetic diversity, endangered species, tropical tree, conservation.

Abbreviation

Abbreviations: SSRs, Simple sequence repeats; STRs, short tandem repeats; CTAB, cetyl trimethyl ammonium bromide; PCR, polymerase chain reaction. ^#These authors contributed equally to this work.