Genetic diversity and differentiation of an endangered tree species, Afzelia xylocarpa (Kurz) craib in Thailand revealed by nuclear microsatellite markers

ABSTRACT: Afzelia xylocarpa is listed as an endangered species on the IUCN World list of Threatened Trees. Habitat loss and over-exploitation for its valuable timber have resulted in a rapid decline of population sizes and local population extinction. Understanding of the processes that determine population genetic structure, gene flow and mating systems is important to conserve and manage existing populations of 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 high genetic diversity (H_S = 0.575) and low 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 high genetic diversity and were less divergent from the other populations. Therefore, these populations should be considered highest priority for conservation of this species.