Taxonomic revision of the genus Chimonocalamus (Arundinarieae, Bambusoideae, Poaceae) in Thailand

Chimonocalamus is a genus in the Arundinarieae (the tribe of temperate woody bamboos), distributed in the Eastern Himalayas, India, Myanmar, China, Thailand, and Vietnam. Distinguishing characters of the genus include pachymorph rhizomes, rings of root thorns at lower culm nodes, a branch complement of 3-5 subequal branches, paniculate inflorescences, and spikelets with 2 glumes and 3-6 florets. Taxonomic knowledge of Chimonocalamus in mainland Southeast Asia has grown as new species were reported from Thailand and Vietnam, adding to those previously documented mainly in China and India. Such a situation supports an increased understanding in the geographic distribution and diversity of the group. The objective of this paper is to update the Chimonocalamus account for Thailand and summarize taxonomic information pertinent to future studies. Here, our taxonomic revision of Chimonocalamus in Thailand includes three species, C. auriculatus, C. elegans and C. gallatlyi; the latter is a new record for Thailand. Nomenclatural treatments, morphological descriptions, a photographic illustration of C. gallatlyi, and a current distribution map of three species are presented.