New oak species found in Guangxi

Oak (genus Quercus), comprising approximately 469 species of ornamental and timber trees and shrubs in the beech family (Fagaceae), is a dominant woody lineage in forest ecosystems across the Northern Hemisphere.

During their herbarium specimens survey of Fagaceae in 2021, researchers from Xishuangbanna Tropical Botanical Garden (XTBG) of the Chinese Academy of Sciences and Yunnan University found some oak materials with characteristics not seen in any known species of Quercus.

After consulting relevant literature and herbarium specimens from major herbaria in China and key international herbaria, they determined that the specimens differ from all published species of Quercus, and represent a new species.

The new species has been named Quercus zhekunii in honor of Prof. Zhou Zhekun of XTBG, a distinguished botanist who has dedicated his career to the systematics, biogeography and fossil history of East Asian Fagaceous plants and has made significant contributions to understanding Cenozoic flora changes in East Asia.

The new species was published in the Nordic Journal of Botany.

Quercus zhekunii is a small evergreen tree or shrub, 2–4 m tall. The dense fused fasciculate and uniserate trichomes on the leaf abaxial surface of Q. zhekunii resemble those of Q. kingiana.

However, its distinctively concave primary and lateral veins on the leaf adaxial surface, along with the prominent backward-recurved leaf blade and leaf margin, make it morphologically distinct from any known species in Q. sect. Ilex.

The new plant fruits biennially (pistillate flowers to acorns requiring two years to mature). It flowers in March and fruits in the next October to early November, and acorns are scarce.

Quercus zhekunii grows on open limestone hills with brown lime soil at elevations of 450–830 m above the sea level. It is found at four known locations on open limestone rocky cliffs, tops or ridges in the northern tropical region of East Asia. It is scattered across western to northwestern Guangxi Zhuang Autonomous Region of China.

"Given its vulnerability to habitat degradation, which significantly impacts its populations in the karst regions of southwestern China, we recommend that Q. zhekunii be classified as 'Endangered' (EN) according to the current IUCN red list categories and criteria," said Professor Huang Jian, corresponding author of the study and a researcher from XTBG.