Gold‐thread nanmu is a highly valuable timber well‐known for its durability, unique special fragrance, and attractive golden color. The main sources for gold‐thread nanmu are species of Phoebe Nees (Lauraceae). Phoebe bournei and P. zhennan have been regarded as the best sources due to their tall and thick trunks and exceptionally high quality timber. However, the delimitation of these two highly valued gold-thread nanmu species has been confusing and debated.
Researchers from Xishuangbanna Tropical Botanical Garden (XTBG) integrated morphology and restriction site-associated DNA sequencing (RAD-seq) to define the species boundaries of P. bournei and P. zhennan.
The researchers delineated the geographic distribution using occurrence data of herbarium specimens and their field investigation, and undertook analyses of morphological features and RAD‐seq data for samples of the P. bournei and P. zhennan complex, representing their entire distributional areas.
They found that the character “extension of cymose panicles” was ambiguous and apparently affected strongly by local growing conditions. They also found that the petioles of P. bournei are thicker than those of P. zhennan.
Leaf shape also differed, with the angle of the leaf apex being acuminate (wider) in P. zhennan and acute in P. bournei.
In general, P. bournei has thicker petioles, narrower leaf, and more prominent tertiary and quaternary veins compared to P. zhennan, thus allowing for more sustainable management of gold‐thread nanmu resources.
The two species are now distinct in distributions except overlapping in the Wuling Mountains.
Central Fujian, southern Jiangxi, the Nanling Mountains, and Wuling Mountains are centers of distribution of P. bournei (abundant); the adjoining eastern regions of the Qionglai Mountains, southern Sichuan hills, and Wuling Mountains contain the best remnants of P. zhennan.
The researchers suggested that the distribution regions should be the priority of conservation areas.
The study entitled “Congruent Species Delimitation of Two Controversial Gold-thread Nanmu Tree Species Based on Morphological and RAD-seq Data” has been published online in Journal of Systematics and Evolution.
LI Jie Ph.D
Center for Integrative Conservation, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla,Yunnan 666303, P. R. China