New Rubiaceae species found in Yunnan, China

Leptomischus is a genus of plants in the family Rubiaceae, which is most abundant in the tropics and includes many economically important members used for purposes such as medicine, horticulture, and food production. Leptomischus is a typically Asian genus found only in Myanmar (one species), India (three species), Vietnam (five species), and China (five species). However, it is a poorly known and small genus, with only 10 species currently recognized.

During a botanical expedition to Yuanyang Guanyinshan Provincial Nature Reserve, researchers from the Xishuangbanna Tropical Botanical Garden (XTBG) of the Chinese Academy of Sciences collected an unknown Rubiaceae species. After extensive examination and comparison within allied groups, morphological comparison with related literature and herbarium specimens, they confirmed that the unknown species was new to science.

The new species was named Leptomischus bracteosus to refer to its distinct bracts. The results were published in Phytotaxa.

Leptomischus bracteosus is a perennial herb. It shares similarities with L. primuloides and L. parviflorus, including similar shape, indumentum, the number of secondary veins on isophyllous leaves, and the inflorescences bearing several distylous flowers. However, it differs from them and other congeners in that it has four bracts and bracteoles that resemble stipules, which are subtriangular to rhombic or broadly ovate with a truncate base, and the calyx limb lobed for about a third.

Leptomischus bracteosus is known only from the type locality at 1,750–1,850 m elevation in Yuanyang County, Honghe Hani and Yi Autonomous Prefecture, Yunnan Province, China. It grows in the moisture along the ravine stream of evergreen broad-leaved forests.

"As only two populations have been found and the population is declining due to forest fragmentation and habitat degradation, we consider the conservation status to be 'Vulnerable' according to the International Union for Conservation of Nature standard," said Tan Yunhong of XTBG.