Development and technical application of SSR-based individual identification system for Chamaecyparis taiwanensis against illegal logging convictions

Abstract

Chamaecyparis taiwanensis is an endemic plant suffering illegal logging in Taiwan for its high economic value. Lack of direct evidence to correlate stump and timber remains a hurdle for law enforcement. In this report, 23 polymorphic Genomic Simple Sequence Repeat (gSSR) and 12 Expressed Sequence Tag (EST)-SSR markers were developed and their transferability was assessed. The individual identification system built from selected non-linkage 30 SSR markers has a combined probability of identity as 5.596 × 10–12 equivalents to identifying an individual in a population of up to 18 million C. taiwanensis with 99.99% confidence level. We also applied the system in an actual criminal case by selecting 19 of these markers to correlate illegally felled timbers and victim trees. Our data demonstrate that molecular signals from three timbers hit with three victim trees with confidence level more than 99.99%. This is the first example of successfully applying SSR in C. taiwanensis as a court evidence for law enforcement. The identification system adapted advanced molecular technology and exhibits its great potential for natural resource management on C. taiwanensis.

SSR individual identification system construction and population genetics analysis for Chamaecyparis formosensis

“…For a higher accuracy of court's judgment on illegal felling, it is necessary to establish a complete forensic system. Although some SSR markers of cypress have been published 17 , 25 – 27 , the reported detection rates for dried timber were only 20–40% 8 , 9 . Therefore, it is necessary to develop more SSR markers as a contingency plan.…”

“…Moreover, timber production countries suffer from illegal felling, particularly in South-east-Asian, African and South American countries 7 . Although suspects were arrested on some occasions, lack of direct scientific evidence to link seized timber and stump had led to a failure of conviction in the majority 8 .…”

“…In recent years, countries suffering from serious illegal logging have successively begun to develop DNA-based timber individual identification systems that can provide court evidence for a conviction. The reported technology for individual identification systems includes DNA point difference-based technique SNP (Single Nucleotide Polymorphism) 9 , and DNA length difference-based techniques SSR (Simple Sequence Repeat) 4 , 6 , 8 , 10 , 11 , and INDEL(Insertion/Deletion). SNP, SSR, and INDEL are all co-dominant molecular markers classified into heterozygous and homozygous.…”

“…When reaching enough numbers of the polymorphic molecular markers, they can be used for individual identification and thus can be used to compare the seized timber to the illegally felled stumps. The reported individual identification systems have demonstrated their potentials to provide scientific evidence for court cases 4 , 6 , 8 – 11 .…”

“…In the illegal felling crime case reports C. taiwanensis 8 and F. excelsior 4 , it is demonstrated that the SSR individual identification system can provide scientific evidence that is considered acceptable by court. In these cases, the individual identification system developed with genetic markers for those species were used to link seized timbers and victim trees, while considering the random probability of the same genotype appearing in the population.…”