Resolving a nearly 90-year-old enigma: The rare Fagus chienii is conspecific with F. hayatae based on molecular and morphological evidence

• Published in: Plant diversity 2023-09, Vol.45 (5), p.544-551
• Main Authors: Li, Dan-Qi, Jiang, Lu, Liang, Hua, Zhu, Da-Hai, Fan, Deng-Mei, Kou, Yi-Xuan, Yang, Yi, Zhang, Zhi-Yong
• Format: Article
• Language: English
• Subjects: China; Conservation; Conspecific; conspecificity; extinction; F. hayatae; Fagus; Fagus chienii; germplasm conservation; Morphology; Phylogenetics; phylogeny; prioritization; rare species; Research Paper; species diversity; uncertainty
• ISSN: 2468-2659; 2096-2703; 2468-2659
• DOI: 10.1016/j.pld.2023.01.003

Taxonomic uncertainties of rare species often hinder effective prioritization for conservation. One such taxonomic uncertainty is the 90-year-old enigma of Fagus chienii. F. chienii was previously only known from the type specimens collected in 1935 in Pingwu County of Sichuan Province, China, and has long been thought to be on the verge of extinction. However, morphological similarities to closely related Fagus species have led many to question the taxonomic status of F. chienii. To clarify this taxonomic uncertainty, we used the newly collected samples to reconstruct a molecular phylogeny of Chinese Fagus species against the phylogenetic backbone of the whole genus using seven nuclear genes. In addition, we examined nine morphological characters to determine whether F. chienii is morphologically distinct from its putatively closest relatives (F. hayatae, F.longipetiolata, and F.lucida). Both morphological and phylogenetic analyses indicated that F. chienii is conspecific with F. hayatae. We recommended that F. chienii should not be treated as a separate species in conservation management. However, conservation strategies such as in situ protection and ex situ germplasm preservation should be adopted to prevent the peculiar “F. chienii” population from extinction. •Fagus chienii is nested with Fagus hayatae in phylogenetic trees inferred from seven nuclear loci.•F. chienii is morphologically indistinguishable from F. hayatae.•F. chienii should not be treated as an independent species in conservation management. Description. Trees up to 20 m tall. Winter buds to 1.5 cm. Leaf petiole 0.3–1 cm long; leaf blade ovate, 3.8–8.4 cm long, 2.1–4 cm broad, base broadly cuneate to acuminate; midvein flexuous toward apex; secondary veins (5) 7–11 on each side of midvein, ending in teeth; teeth 0.3–1 mm long. Peduncle 0.5–1.8 (−2) cm, pilose. Cupule 6–13 mm long; bracts linear, recurved, pilose, 0.1–4 mm long. Nut as long as cupule, with very small wings near apex.