Shorea platyclados is a Southeast Asian tropical montane species with great potential for timber utilization. There is no information about the genetic structure and population variability available for this species, yet the region harbors most of the unlogged populations of this timber wood species. The relative abundance and intactness of most of the natural populations offer a potential use of this species as a modal species for developing tests useful for illegal logging of timber and tracing the population of origin. In this study, we used six highly polymorphic microsatellite loci on 159 S. platyclados individuals. The ability to confidently identify or exclude a population as the source of an individual was exploited by using different well-established assignment methods i.e., Bayesian, Frequency, and Distance-based methods.  Although several alternative methods have been developed for this purpose are yet to be fully evaluated with empirical data.  Specimens from the unknown population (n=20), its known source population (n=34) and two other populations from the same geographical region (Kelantan=54; Fraser=51) were genotyped for 6 loci. The results obtained from self-assignment of individuals from all four populations identified Bayesian and Frequency methods as the most consistent and accurate, which correctly assigned 85-96% of individuals. Performance was variable among the distance-based methods, with Das (shared allele distance), Nei DA, and CavalliSforza performing best, whereas Goldstein (δµ)² consistently performing poorly. Using these methods, we attempted to determine the source of S. platyclados individuals. Results obtained based on Frequency and Bayesian methods assigned 50-55% of individuals to the source population, the remainder of individuals were either assigned to other populations or were not assigned to any of the sampled populations. Low levels of assignment observed reasoned mainly due likely to low levels of genetic differentiation (Fst = 0.028 – 0.052) because of a high rate of gene flow observed between contiguous populations. Population genetic differentiation seems directly related to the high accuracy of individual assignment. Strategies to improve assignment frequency and power of discrimination were further discussed.

Keywords: Illegal Logging; DNA markers; Population Genetics; Timber Tracking; Timber Certification