Chimonocalamus auriculatus Sungkaew, Hodk. & N.H.Xia, 2018

Sungkaew, Sarawood, Hodkinson, Trevor R., Xia, Nianhe & Teerawatananon, Atchara, 2018, Chimonocalamus auriculatus, one more new temperate woody bamboo species of the genus (Poaceae: Bambusoideae: Arundinarieae) described from Thailand, Phytotaxa 357 (1), pp. 66-70 : 67-70

Chimonocalamus auriculatus Sungkaew, Hodk. & N.H.Xia , sp. nov. ( Figs. 1 & 2 )

Diagnosis:— Chimonocalamus auriculatus most closely resembles C. montanus Hsueh & Yi (1979: 79) and C. makuanensis Hsueh & Yi (1979: 80) but differs in its conspicuous deltoid lobed auricles which have margins fringed with several persistent bristles ( Table 1 ).

Type:— THAILAND. Phitsanulok province: Chat Trakan district, Bo Phak, Phu Soi Dao National Park, Lan Son camping area , 17°73’61’’ N, 100°99’22’’ E, elev. 1589 m, 1 September 2012, S. Sungkaew, A. Teerawatananon & W. Sajia 1503 (holotype: BKF! ; isotypes: BK! , IBSC! , Natural History Museum, Thailand!).

Description:—Arborescent bamboo. Rhizomes pachymorph with short necks, forming a clump of culms. Culms erect, 5 − 7 m tall, 1 − 3 cm in diam., green and covered with white to gray hairs when young, yellowish-green and glabrous when mature; nodes faintly prominent, glabrous, the basal nodes (from the ground level to nodes 10 − 15) with a ring of 1 − 7 mm long root-thorns; internodes terete, 10 − 27 cm long, walls thin, 2 − 5 mm thick (mid-culm portion). Branches developing from around the mid-culm upwards. Mid-culm branch complement with 3 sub-equal branches at each node, the middle branch slightly bigger than the 2 side-branches. Culm leaf sheath green, deciduous, 17 − 26 × 7 − 10 cm, mottled or blotched when dry, covered abaxially with sparsely appressed brown to dark brown hairs, apex slightly concave to truncate, 5 − 10 mm wide, margins glabrous; auricles prominent, deltoid lobed, 1.5 − 3 mm tall, oral setae several, persistent, 0.3 − 1 cm long; ligule truncate to slightly concave, 2 − 3 mm tall, margin irregular toothed to fimbriate and fringed with minute cilia; blades purplish-green to green, spreading to slightly recurved, lanceolatelinear, 3 − 10 × 0.2 − 0.5 cm. Foliage leaves 3 − 7 per ultimate branch; sheaths 2 − 3.5 cm long, glabrous, margins glabrous; auricles prominent, deltoid lobed, 0.25 − 0.5 mm tall, oral setae 5 − 9, persistent, 2 − 5 mm long; ligules convex to slightly truncate, membranous, 0.5 − 1 mm tall, margin irregular toothed to fimbriate; pseudo-petiole 0.1 − 0.2 cm long; blades with inconspicuous transverse veins, narrowly lanceolate, 5 − 11 × 0.5 − 0.9 cm, glabrous both sides, occasionally abaxially sparsely hairy on nerves (particularly those nerves near the blade margins), base acute to attenuate, apex acuminate. Inflorescence unknown.

Etymology:—The specific epithet auriculatus refers to the deltoid lobed culm leaf sheath auricles which clearly distinguish the new species from all the other Chimonocalamus species by having a permanent fringe of long bristles.

Ecology and distribution:—Currently, it is only known from Phu Soi Dao National Park in northern Thailand. It grows in moist soils in the understory of montane forest and along streams between 1500 m and 1800 m elevation. So far, Chimonocalamus auriculatus represents the southernmost species of the genus.

Conservation status:— Chimonocalamus auriculatus is restricted to a narrow elevation belt with good forest cover on the Phu Soi Dao mountain. The new species is known from only two populations, both of which occur in a protected area. According to the IUCN Red List criteria ( IUCN 2016), this bamboo could be assigned to a category of Vulnerable (VU) D2 based on its limited area of occupancy and the low number or known populations. However, insufficient data exists regarding its distribution, so we provisionally propose the species conservation status as Data Deficient (DD).

Additional specimens examined:— Thailand. Phitsanulok, Chat Trakan district, Bo Phak, Phu Soi Dao National Park, Lan Son camping area , 17°73’61’’ N, 100°99’22’’ E, elev. 1589 m, 1 September 2012, S. Sungkaew, A. Teerawatananon & W. Sajia 1504 ( BKF!, BK!, IBSC!, Natural History Museum, Thailand!) .

Figures

FIGURE 1. Chimonocalamus auriculatus.A. Abaxial surface of a whole culm leaf; B. Portions of culm leaves, showing adaxial surface (left) and abaxial surface (right); C. Shoot; D. Portion of culm showing bud complement and nodes with a ring of root-thorns; E. Leafy branch. Drawn from S. Sungkaew, A. Teerawatananon & W. Sajia 1503 (BKF) by A. Teerawatananon.

FIGURE 2. Chimonocalamus auriculatus A. Habit; B. Foliage leaves; C. Young culm showing nodes with a ring of root-thorns; D. Branch complements; E. Clump habit; F. Shoot, showing deltoid lobed auricles with oral setae. Photos by A. Teerawatananon.