Dendrobium mizanii R.Go et E.E. Besi, 2018

Dendrobium mizanii R.Go et E.E. Besi View in CoL , sp. nov. ( Figure 1 View FIGURE 1 and 2 View FIGURE 2 )

Type:— MALAYSIA. Terengganu: Setiu. ca. 1,300 m, 15 June 2017, Besi et al. EDW004 (holotype: UPM!) ; MALAYSIA, Terengganu, Setiu , ca. 1, 300 m, 30 April 2018, Besi et al. EDW044 (isotype: UPM!) .

Diagnosis:— This species is very identical to D. crocatum Hook.f. , a widely distributed species in Malaysia and Thailand, by having the plant almost similar morphologically with the stems slender, green-purplish, leaves lanceolate, flowers spreading with tip reflexed, and lip widely canaliculate but it clearly differs from the latter by having the lip 3- lobed, blade almost in the same length as the column (in natural position), midlobe widely rounded with apex decurved (curved downwards) and margin copiously undulate and crenate; mentum slightly bent downward; and roots distinctly thicker about 3 mm wide, white and covered with velamen. It shares similarities with D. doloissumbinii J.J. Wood on its stems up to 40 cm long, lip yellowish-green in with reddish-purple speckles and the midlobe apex wide, slightly decurved, but it differs by having the flower (less than 4 cm long) smaller, mentum (less than 2.5 cm long) shorter, and the lip distinctly 3-lobed with the apex copiously undulate. The D. doloissumbinii is also having blade much longer in length than the column (in natural position), similar to that observed in D. crocatum and other species in Sect. Calcarifera , including D. subflavidum Ridl. and D. lankaviense Ridl .. A detailed comparison between D. mizanii and D. doloissumbinii is provided in Table 1.

Description:— Plants epiphytic and terrestrial. Roots 3 mm thick, white, completely enveloped by velamen. Stems up to 35–45 cm long, ca. 0.5 cm wide, leafy at the distal portion; internodes 2.3–4 cm long. Leaves 7.4–10 × 1.6–2 cm, about 2 cm apart, lanceolate, apex oblique, acute. Racemes hanging, borne from the upper nodes of both leafy and leafless stems, 2 to 3-flowered. Flowers ca. 3.8 × 3.5 cm, not scented, yellowish-green in general with petals and sepals almost entirely white, petals and sepals with a prominent median vein; lip yellowish-green in general with reddish-purple speckles; petals and sepals spreading and slightly reflexed after two days blooming period. Flower buds narrowly spathulate with base slightly decurved (curved downwards). Mentum ca. 2.1 cm long, whitish to yellowish green at the apex, widely conical, laterally compressed, gradually tapering towards apex; apex obtuse, slightly decurved. Pedicel-with-ovary ca. 1.6 cm long, narrowly clavate. Dorsal sepal 1.5 × 0.8 cm, oblong to ovate, acute. Lateral sepals 2.7 × 0.8 cm, spathulate, ovate apically, acute, margin entire; free portion ovate, acute, 1 cm long, 0.7 cm wide at the base; unfree portion narrowly clavate 1.7 cm long, 3.5 mm wide at the base. Petals 1.5 × 0.5 cm, oblong to obovate, apex widely acute, margin entire. Lip yellowish-green with flushed darker yellowish at the central disc, irregular-sized reddish-purple spots at the interior and along the margin of the side lobes; ca. 3.5 × 1 cm in natural position, 3.5 × 1.3 cm when flattened; 3-lobed, widely spathulate in general outline, firmly and widely clawed at the base; 2 cm long indistinct glabrous keel at the median part extending from the base of the claw towards the base of the midlobe; disc ca. 1 × 0.35 cm; midlobe ca. 6 mm × 9 mm when flattened, widely rounded with apex straight when at young stage and widely decurved at matured stage, very shortly bilobulate, widely cleft in the middle with a minute sinus, margin copiously undulate; side lobes 2 mm long, free, semi-circular, obliquely rounded tips, strongly raised and curved inward, margin entire to crenate at the edges with a minute sinus at the junction with the midlobe; claw ca. 1.5 cm long, 3 mm wide at the base (unflattened), widely canaliculate, margins erect and widely raised like a gutter with basal jointed to a rounded end, a median keel in the middle extending towards the base of the midlobe. Column ca. 3 cm long including stelidia and foot, greenish with tip darker yellowish, narrowly clavate, yellow entirely; apex ca. 1 cm long including stelidia, 5 mm cm wide; rostellum with triangular acute, erect, pointing tip at the base; stelidia 1 mm long, oblong with retuse tip; foot ca. 2 cm long, 3 mm wide at the apex, slightly tapered towards base; anther-cap ca. 3.7 × 3.5 mm (described from a spirit-preserved material), oblong, cucullate, entire to minutely ciliate at the basal margin, whitish yellow; pollinia 4, paired, ca. 2.5 × 1.1 mm, pyriform (described from a spirit-preserved material), light yellowish. Seed capsule not seen.

Etymology:— This species is named after His Majesty Sultan of Terengganu, Tuanku Mizan Zainal Abidin. To commemorate His Majesty’s continuous dedications towards conservation ventures in Terengganu.

Phenology:— The flowering period under ex-situ acclimatization is April, June and August. The flowers show a significant variation between the first day and the days onwards of the blooming period, where the lip apex would appear straight and the mentum straight with sharp tip in the first day, and the lip apex gradually decurved (curved downwards) and the mentum slightly wider with the apex decurved and obtuse in the following days.

Distribution and Ecology:— The earliest specimen (holotype) was found in a summit of a montane forest in Setiu, Terengganu, at about 1,300 m above sea level, and growing terrestrially at the moist humus at the base of a tree. Then, the second specimen (isotype) was collected from the same area, but growing epiphytically on a medium-sized phorophyte tree.

Additional Specimens Examined:— MALAYSIA. Terengganu: Setiu. ca. 1,300 m, 15 June 2017, Besi et al. ED/DOME 028 (living specimen: UPM).

Tentative key to the species of Dendrobium Sect. Calcarifera from Peninsular Malaysia with raceme 2-4 flowered; lip widely canaliculate, blade not bent and parallel to column with 1 indistinct or not raised keel at the central part extending from base of the claw towards the apex, apex slightly decurved (curved downwards); mentum long, more than 1.5 cm long; including D. doloissumbinii from Borneo.

1 Stems only up to 45 cm long..............................................................................................................................................................2 Stems about 60 to 70 cm long............................................................................................................................................................3

2 Lip without side lobes; midlobe shortly narrowed with apex emarginate; margin entire to minutely crenate..................................4 Lip with side lobes; midlobe widely rounded with apex straight when at young stage and widely decurved at matured stage, very shortly bilobulate, widely cleft in the middle with a minute incision; margin copiously undulate..................................... D. mizanii

3 Lip apex slightly notched; margin crenate .................................................................................................................. D. subflavidum Lip apex trilobulate; margin crenate to undulate.............................................................................................................. D. crocatum

4 Lip apex broadly rounded, slightly notched; blade glabrous ....................................................................................... D. lankaviense Lip apex shortly narrowed, widely cleft; blade ecallose ......................................................................................... D. doloissumbinii

Proposed conservation status: —As for a preliminary view on its conservation priority, authors would suggest that this species should be classified as “critically endangered” [CR B2(a)], in accordance to the IUCN Red List Categories and Criteria version 13 (March, 2017). Until now, it has only been collected from a single locality in Peninsular Malaysia, confined to a montane forest area with a mildly disturbed environment. This mountain is renowned and actively visited by tourist and local people for hiking and other recreation activities that has projected in a drastic disturbance towards its vegetation, especially in the summit area. Therefore, the exact locality is withheld in this paper to protect the populations.