Origin and diversification of Aquilaria (Thymelaeaceae): inferences from a phylogenetic study based on matK sequences

In the realm of Aquilaria classification and grading, a persistent market uncertainty persists, questioning whether the basis should be geographical distribution or biological origin. In this study, our goal is to shed light on the origin and diversification of the Aquilaria genera. We collected and analyzed a total of 320 specimens belonging to 25 species within the Aquilaria genera. Noteworthy findings include observed leaf similarities among three distinct species— A. yunnanensis , A. sinensis , and A. beccariana . Further results emphasize the effectiveness of matK molecular markers in differentiating Aquilaria species, leveraging 8 stable polymorphic loci. The integration of matK and trnL-trnF not only validates this efficacy but also streamlines the systematic categorization of 34 agarwood products. Delving into the evolutionary status and genetic background of Aquilaria , this study employs molecular clock analyses, revealing four distinct pedigrees: the Chinese pedigree 1 and 2, the Indonesian pedigree, and the Indochina pedigree, aligning with A. sinensis , A. malaccensis , and A. cumingiana , respectively. Notably, we identified A. sinensis and A. malacca as part of the youngest branch of Aquilaria evolution, with A. hirta emerging as the oldest member dating back to 6.78 million years ago. Furthermore, the research challenges previous assumptions by reevaluating G. walla , placing it at 5.75 million years ago, and suggesting its incorporation within the Aquilaria genus rather than considering it as an early divergent species.