﻿Yersinochloanghiana, a new species (Poaceae, Bambusoideae, Bambuseae) from southern Vietnam

﻿Abstract Yersinochloanghianasp. nov. from Vietnam is described and illustrated. It is found from southern Vietnam, where it occurs at an elevation of 1130 m in Braian Mountain, Di Linh District, Lam Dong Province. This new species is distinguished from a similar species, Yersinochloadalatensis, by culm nodes with a thick swollen patella, culm leaf blades erect, auricles conspicuous, margins bearing long hairs, palea dorsal view showing rachilla extension and rudimentary floret at the apex and lodicules bifid at the base.

During our investigation of the bamboos from Braian Mountain, Di Linh District, Lam Dong Province, in southern Vietnam in December 2007, the authors found several populations of a clambering bamboo widespread and abundant through the degraded natural forest in valleys between 1100 and 1130 m a.s.l. Specimens of rhizomes, branches, culm leaves and flowers were collected and studied. We confirmed the presence of inflorescences terminating at leafy branches, pseudo-spikelets having only one perfect floret with no terminal vestigial flowers, the palea unkeeled and the anther apex bearing tiny spines, as was found in Yersinochloa dalatensis. However, further detailed studies differentiated this specimen from the latter by characters having culm nodes with a thick swollen patella; culm leaf blades erect, swollen at the base; auricles conspicuous, margins bearing long hairs; palea dorsal view of palea showing rachilla extension and rudimentary floret at the apex; lodicules bifid at the base (Table 1,  . Besides that, the species is distinguished from Cochinchinochloa, because it has only one perfect floret, a terminal vestigial flower absent and anther apices bearing tiny spines. Its flower is typical in Yersinochloa. Otherwise, the culm leaf blades of Cochinchinochloa braiana have embraced the entire internode, auricles triangle-shaped, while the species have only half embraced the internode. Thus, it is not close to Cochinchinochloa braiana. These distinctive features indicate that this bamboo is readily diagnosed as a new species.

Materials and methods
This study is based on plant material collected from Braian Mountain, Di Linh District, Lam Dong Province, in southern Vietnam. The plant specimens were deposited at DLU, VNMN and VTN-Tay Nguyen Institute for Scientific Research. Vegetative parts were measured in the field; fresh flowers were examined under a light-microscope and colour photographs were taken using a camera. Other similar species were used for critical comparison.
Description. Culms and branches scrambling or hanging over nearby vegetation or trees, 5-10 m tall; internodes 40-80 cm long and 3.5-4.5 cm in diameter; when young, densely covered with appressed white hairs; culm walls 0.8-1.0 mm thick; nodes with a thick swollen patella. Branches several with middle one dominant, elongating. Culm leaves black-purplish, sheath with dense appressed white hairs on the abaxial surface; 25-28 cm long and 10-12 cm wide at base; apex 7-8 cm wide and truncate; margins     Local uses. Yersinochloa nghiana is of considerable importance to the local people. Its culms are used for making handicrafts and household tools.
Etymology. The new species is named in honour of Dr. Nguyen Hoang Nghia for his contributions to the bamboo research in Vietnam.
Preliminary conservation status. The species Yersinochloa nghiana sp. nov. is only known from a single population in Braian Mountain, Di Linh District, Lam Dong Province, Vietnam. This single population has no more than 500 mature clumps, all growing in degraded natural forests in valleys, but is also common along rivers and valleys. According to IUCN Red List Categories and Criteria (IUCN 2022), the species is classified as data deficient (DD) and it needs more surveys.