Desmodium brevipedicellatum W.Saisorn, Chantar. & Balslev, 2016

Saisorn, Witsanu, Balslev, Henrik & Chantaranothai, Pranom, 2016, A new species of Desmodium (Leguminosae; tribe Desmodieae) from Thailand and Laos with two new distribution records and lectotypifications for Thailand, Phytotaxa 263 (2), pp. 154-160 : 154-159

Desmodium brevipedicellatum W.Saisorn, Chantar. & Balslev , sp. nov. ( Figs. 1 − 3A )

D. brevipedicellatum is similar to D. auricomum Graham in Wallich (1831: 196) ex Benth. (1852: 223) but differs in having an erect habit, narrowly elliptic to oblong leaflets, short pseudoracemose inflorescences with very dense flowers, persistent primary bracts, very short pedicel, larger flowers, calyx teeth prominently longer than the corolla, keels equal to the wings, shorter stamens, 3-ovules, and 1–3-pod articles ( Table 1).

Type:— THAILAND. Sakon Nakhon: Phu Phan National Park , dry dipterocarp forest, 271 m, 17°3´23.43´´ N, 103°57´50.50´´ E, 19 October 2014, W. Saisorn 264 (holotype KKU!; isotypes AAU!, BK!, BKF!) .

Herbs 0.1–0.5 m high, erect with a single to many branches; stem and twig terete, sparsely appressed hairy on lower part and more densely appressed hairy on upper part. Leaves spirally arranged, trifoliolate or rarely mixed with unifoliolate leaves on lower part of stem; stipules narrowly triangular, 4–7 × 0.8–1.0 mm, free, persistent, apex long pointed, surface whitish appressed hairy; petioles 3–10 mm long, appressed pubescent; rachis 1.5–3.0 mm long, appressed pubescent. Leaflets subcoriaceous; stipels filiform, 1.5–2.5 mm long, apex pointed, hairy; petiolules ca. 1 mm long, appressed pubescent. Terminal leaflet narrowly elliptic to oblong, 1–3 × 0.5–1.0 cm, apex shallowly emarginate to obtuse, base obtuse, margin entire, upper surface glabrous to sparsely appressed pubescent, lower surface sparsely to densely appressed pubescent; lateral veins 4–7 per side, not reaching the margin. Lateral leaflets narrowly elliptic to oblong, 0.5–2.0 × 0.3–0.6 cm, apex shallowly emarginate to obtuse, base cuneate to obtuse, margin entire, upper surface glabrous to sparsely appressed pubescent, lower surface sparsely to densely appressed pubescent; lateral veins 5–7 per side, not reaching the margin. Inflorescences very dense-flowered, shortly and densely pseudoracemose, ca. 1 cm long on lateral branches, in the upper axils, or up to 5 cm long on terminal shoots; rachis densely appressed hairy, ca. 1 mm long. Primary bract ovate, 4–6 × 1.5–3 mm, apex long acuminate to caudate, abaxially appressed pubescent, adaxially glabrous, enclosing 2-immature flowers, persistent. Secondary bract absent. Flowers 7–8 mm long, in 2- flowered fascicles; bracteole absent; pedicels 0.5–2.0 mm long, appressed pubescent and minutely uncinate, ca. 0.1 mm long. Calyx light green, 7–8 mm long, base cuneate; tube 1.0– 1.5 mm long, outside minutely uncinate, inside glabrescent; teeth 5, equal, 5–6 mm long, prominently longer than tube length and corolla length (2–4 mm long), outside long and densely pubescent (1–2 mm long), inside appressed pubescent, shorter than outside. Corolla pink to light purple; standard elliptic to oblanceolate, 3.7–4.0 × 1.5–1.8 mm, apex rounded, base attenuate, not auriculate, claw 0.3–0.5 mm long; wings slightly oblong, 3–4 × 0.8–1.0 mm, apex obtuse, base auriculate, ca. 0.1 mm long, claw 0.5– 0.8 mm long; keels incurved, 3.5–4.0 × 0.8 mm, equal to wing length, apex obtuse, base auriculate, ca. 0.1 mm long, claw ca. 1.8 mm long. Stamens 3.0– 3.5 mm long, vexillary stamen completely free, other stamens united, upper free parts of filaments alternately longer or shorter; anthers elliptic, ca. 0.3 × 0.2 mm. Gynoecium 4.0– 4.5 mm long; ovary sessile, oblong, laterally compressed, pubescent, 3-ovulate; style ca. 2 mm long, sparsely pubescent; stigma minutely capitate. Pods brown, sessile, dehiscent along lower suture, loment, 1–3-articulate, straight or slightly curved, 5–7 × 2.0– 2.5 mm, with the band of densely whitish hairs on lateral surfaces, upper suture thickened, slightly straight, lower suture thickened, more constricted than upper, ca. 0.8 mm deep, isthmus ca. 3/5 as broad as the pod; articles slightly quadrangular to elliptic, 2–3 mm long; fruiting pedicels 1.5–2.0 mm long, appressed pubescent and minutely uncinate. Seeds reddish brown, reniform, 1.3–1.5 × 1.0–1.1 × 0.5 mm.

Distribution:— Thailand (Sakon Nakhon, Si Sa Ket) and Laos (Phou Khao Khouay National Biodiversity Conservation Area).

Ecology:—In open places and near small streams in dry dipterocarp forest; 220 − 600 m.

Phenology:—Flowering between September and December.

Etymology:—The specific epithet refers to the short pedicel.

Vernacular:— None nay noi (Laotian); Waen khok kan san (Thai).

Conservation status:—Using the IUCN Red List Categories and Criteria (IUCN: 2012), we designate D. brevipedicellatum as Vulnerable (VU) in accordance with criteria D1 and D2. We counted mature individuals of two populations at Phu Phan National Park and Phanom Dong Rak Wildlife Sanctuary and found that numbers of mature individuals of each are fewer than 1,000 plants (D1). Moreover, this species has a very restricted area of occupancy (less than 20 km 2) and numbers of locations are fewer than five places (D2).

Notes:— Six specimens of D. brevipedicellatum were collected from north-eastern and eastern regions of Thailand and one from Laos. We found a few individuals in Phu Phan National Park, Sakon Nakhon Province (north-eastern region) and Wang Yai Waterfall, Phanom Dong Rak Wildlife Sanctuary, Si Sa Ket Province (eastern region). They grow in open places or near small streams in dry dipterocarp forest. This species is similar to D. auricomum in the presence of a dense band of whitish hairs on the lateral surfaces of pods, deeply divided calyx teeth, and dense cover of hairs on the outside of the calyx. Additional characters that separate the two species are listed in Table 1.

Additional specimens examined:— THAILAND. Sakon Nakhon: Phu Phan National Park , 1 November 1998, C. Leeratiwong 98−32 (KKU), 5 January 2016, W. Saisorn 425 (KKU) & 6 January 2016, W. Saisorn 428 (KKU) ; Si Sa Ket: Khun Han, Phanom Dong Rak Wildlife Sanctuary , 600 m, 22 December 2003, J.F. Maxwell 03−388 (CMUB) & 219 m, 26 January 2016, W. Saisorn 446 (KKU) . LAOS. Phou Khao Khouay National Biodiversity Conservation Area, 220 m, 11 September 2005, K. Chanthavongsa 18 (KKU) .

Desmodium concinnum DC. (1825: 101) . Type:— NEPAL, Wallich s.n. (holotype G, fide Dy Phon, Ohashi & Vidal 1994). ( Fig. 3B )

Meibomia concinna (DC.) Kuntze (1891: 197) .

Hedysarum retusum D. Don (1825: 243) . Type:— NEPAL, at Narainhetty, Hamilton-Buchanan s.n. (holotype BM BM000521602).

Desmodium retusum (D.Don) Sweet (1826: 479) .

Desmodium penduliflorum Wall. (1831: 196) ex Benth. (1852: 224) . Type :— NEPAL, 1821, Wallich no. 5727A (lectotype K-W, designated here; isolectotypes K K001121884 & K K001121885 & BM BM000521678).

Desmodium amoenum Wall. (1831: 196) ex Benth. (1852: 224) . Type:— Wallich no. 5726 (lectotype K-W, designated here; isolectotypes K K000858782, K K000639655 & K K000639656).

Desmodium barbigerum Lév. (1916: 153) . Type:— CHINA. Yunnan: Ou Long-Mo et Ma Gan Chan, 2550 m, July − August 1911 –1912, E.E. Maire s.n. (fide Ohashi 1973).

Distribution:—Himalaya (north-eastern and north-western India, Nepal, Sikkim and Bhutan), China, Myanmar, Thailand (Loei), Laos and Vietnam.

Ecology:—In evergreen forest on mountain slope.

Phenology:—Flowering in November.

Vernacular:— Ma hae (Thai) .

Notes:—This species was known from the Himalayan range, Laos and Vietnam. We discovered a few specimens

[Y. Hanmontri 10 (KKU) and S. Mattapha s.n. from Loei Province, Thailand] that represent the first record of the species from Thailand. The four sheets of the type collection, Wallich no. 5727A of D. penduliflorum are kept at BM, K and K-W and the four sheets of the type collection, Wallich no. 5726 of D. amoenum are kept at K and K-W. Lectotypes of each synonym from K-W was selected here because it was well preserved.

Specimens examined:— THAILAND. Loei:Phu Ruea, Phu Ruea National Park, 12 November 2005, Y.Hanmontri 10 (KKU) & 11 November 2002, S. Mattapha s.n. (KKU no. 7814).

Desmodium laxiflorum DC. (1825: 100) subsp. lacei (Schindl. 1926: 261) H. Ohashi (1973: 103) . ( Fig. 3B )

Desmodium lacei Schindl. Type :— MYANMAR. Taungoo district: Saing Yani Reserve, 152 m, 14 December 1909, J.H. Lace 5027 (holotype K K000858871; isotype E E00301249).

Distribution:— Myanmar and Thailand (Lamphun, Tak).

Ecology:—In deciduous forest and forest on limestone; 500–550 m.

Phenology:—Flowering in September.

Vernacular:— Tuet ma (Thai).

Notes:—The Thai specimen extends the range of this subspecies from Myanmar eastward to northern Thailand.

Specimens examined:— THAILAND. Tak: Umphang, Ti Lo Su Waterfall, 8 October 2014, S. Mattapha 266 (KKU), Lamphun: Mae Tha, Doi Khun Tan National Park, 550 m, 29 September 1994, J.F. Maxwell 94−1055 (BKF, CMUB, L) & Tak: Mae Sot, Wat Tham Manora, 500 m, 16°14´42´´N, 98°39´17´´E, 11 September 2009, D.J. Middleton & P. Triboun 4855 (BKF).

Figures

FIGURE 1. Desmodium brevipedicellatum: A. leaf; B. inflorescence; C. flowers and D. infructescence (photos by the first author from type locality).

FIGURE 2. Desmodium brevipedicellatum: A. habit; B. upper leaf surface; C. lower leaf surface; D. primary bract; E. flower; F. calyx (dissected); G. stamens; H. gynoecium; I. petals: standard (st), wing (wg) and keel (kl); J. pod and K. seed; scale bars A. 1 cm and B.−K. 1 mm (drawn by the first author from W. Saisorn 264).

FIGURE 3. Distribution maps: A. Desmodium brevipedicellatum (Thailand and Laos) and B. D. concinnum, closed triangle and D. laxiflorum subsp. lacei, closed circle (Thailand).