PJB-2019-929
Illegal logging and timber certification: A case for DNA markers
ASIF MUHAMMAD JAVED
Abstract
Illegal logging is one of the major causes of deforestation, forest degradation and depleting genetic diversity, and fluctuating timber market. Conventionally timber inventory is maintained through paper trail thus can easily be forged. Similarly, timber poachers can sell their product as legitimate in the market as there is no way to trace the legality of the timber. Therefore the development of foolproof timber testing tools is necessary to control illegal timber extraction activities. DNA markers could offer the potential to test the legitimacy of the timber in question. Shorea platyclados is locally known as “Dark Red Meranti” is a Southeast Asian tropical montane species with a great potential for timber utilization. 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 timber certification and population origin. In this study, we used six highly polymorphic SSR 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. 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 the individual from all four populations identified Bayesian and Frequency methods as the most consistent and accurate, which correctly assigned 85-96% of individuals to their populations of origin. Performance however was variable among the distance-based methods, with Das (shared allele distance), Nei DA and Cavalli-Sforza performing best, whereas Goldstein (δµ)2 consistently performed 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% individuals to the source population, remainder 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) as a result of the high rate of gene flow observed between contiguous populations. High accuracy was achieved between distant populations due to limited gene flow. Population genetic differentiation seems directly related to the high accuracy of individual assignment. The number of individuals assigned accurately showed their potential to be used in curbing illegal logging. The use of more polymorphic DNA markers would increase the power of assignment tests. Strategies to improve assignment frequency and power of discrimination were further discussed.
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