Validation of ITS barcode for the identification of CITES Malagasy Dalbergia (Fabaceae) species

Abstract

The precious Malagasy rosewood species of the genus Dalbergia have been listed in Appendix II of CITES due to illegal logging and timber trade. Accurate identification and proper delimitation are of paramount importance for endangered species regulated by CITES. One of the most accurate methods of identifying precious woods is DNA barcoding which is a technique for rapid and accurate species identification based on a short DNA sequence or a few DNA regions. Recent studies have shown that the ITS barcode can identify Malagasy Dalbergia species, but the number of species has been limited. In this research study, a total of 136 nuclear ribosomal internal transcribed spacer (nrITS) DNA sequences representing 41 species of Malagasy Dalbergia were used to assess the effectiveness of the ITS barcode in species identification. Each sequence was evaluated by genetic distance and tree-based methods. Using clustering analyses, estimating genetic distances, and comparing sequences of 136 samples, we were able to distinguish species. The interspecific distance was greater than the intraspecific distance, but no barcoding gap was observed. It was found that ITS has a very high discriminatory power for Malagasy Dalbergia species using both NJ and TaxonDNA methods. Considering the "Best Match" and "Best Close Match" analyses, the discrimination powers of ITS were 98.54% and 93.40%, respectively. Our research indicates that the use of ITS as a barcode enables the identification of Malagasy Dalbergia species and contributes to completing the reference library for controlling the trade in precious woods. These results are essential to ensure effective enforcement of regulations and promote the long-term conservation of these species.