Vincetoxicum stewartianum S.A. Shah, 2021

Shah, Sayed Afzal, Sultan, Amir, Wen, Jun, Ullah, Zahid, Nisa, Surat Un, Ren, Zhumei, Alam, Muhammad Maqsood, Iqbal, Javed & Mumtaz, Abdul Samad, 2021, Taxonomy of Vincetoxicum s. str. (Asclepiadoideae, Apocynaceae) from southern Asia including three new species and resurrected names, PhytoKeys 179, pp. 35-73 : 35

9. Vincetoxicum stewartianum S.A. Shah sp. nov. Figs 2Y, Z , 3J , 4P , 6 , 14

Diagnosis.

Differing from V. arnottianum by having retrorse indumentum on the stems, ovate to elliptic-ovate leaves, light purple flowers, and large rhomboid (1 × 1 mm) corona lobes that exceed the gynostegium in length. In V. arnottianum , the indumentum is extrorse on the stems, leaves are mostly narrowly ovate or lanceolate-ovate, flowers dark purple, and corona lobes are deltoid-rhomboid and do not exceed the gynostegium in length.

Type.

India. Uttarakhand: Landour, Mussoorie , 6-7000 ft. 8 August 1938, R.R. Stewart 16709 (Holotype: RAW!) .

Undershrubs, ca. 50 cm tall. Stem striate, pubescent all around, trichomes retrorse, internodes 1.5-5 cm long. Leaves opposite, petiolate; petioles 2-15 mm long, sparsely pubescent all around; lamina discolorous, ovate- or elliptic-lanceolate to narrowly ovate, 5-7.5 × 2-3 cm; apex acute to obtuse sometimes mucronulate; base obtuse to sub-obtuse; veins visible on both sides, secondary veins 8-14 on each side of midrib, both adaxial and abaxial surfaces of lamina glabrous to sometimes sub-glabrous, veins on both surfaces and margins pubescent. Inflorescences sessile; pedicels 2-3 mm long, pubescent along a narrow longitudinal line; bracts narrow tapering, pubescent. Flowers light purple, ca. 5 × 2 mm; sepals tapering to acute apices, up to 2 mm long with ciliate margins, calycine colleters single; corolla tube ca. 1 mm long, lobes oblong, narrowly tapering, ca. 3 × 1-2 mm, bearded within; corona lobes rhomboid, ca. 1 × 1 mm, exceeding the length of the gynostegium, divergent. Follicles and seeds unknown.

Distribution and habitat.

Endemic to eastern Himalayan Mountains of India. The elevation range is 6000 to 7000 m. The limited herbarium materials do not provide more information.

Phenology.

Vincetoxicum stewartianum flowers and fruits from August to September.

Provisional conservation status.

Data deficient (Table 1 ). Vincetoxicum stewartianum is gathered from only the type locality. Besides label data on gatherings from the type locality, information is lacking about its present occurrence. A survey on its occurrence and ecology is recommended.

Etymology.

Named after the collector Prof. R.R. Stewart.

Notes.

The specimens of this species were hitherto misidentified as V. glaucum and V. canescens .

Specimens examined.

India. Himal. Bor. Occ.; Regio temp., s.d., T. Thomson s.n. (GH [GH01147533]; GOET [GOET020096]).

Figures

Figure 2. Outlines of leaves of southern Asian Vincetoxicum. All illustrated specimens are housed at RAW. The first image in each pair corresponds to the adaxial surface and the second to the abaxial surface. All leaves have been taken from the middle of the stem A, B Vincetoxicum sp. aff. arnottianum from S. A. Shah SAS- 9 C, D Vincetoxicum sp. aff. arnottianum from S. A. Shah SAS- 46 E, F Vincetoxicum sp. aff. arnottianum from R. Khan SAS- 41 G, H V. arnottianum from S. A. Shah & F. Rahman SAS- 3 I, J V. arnottianum from S. A. Shah & B. Ali SAS- 4 K, L V. cabulicum from D. Podlech 15814 M, N V. cardiostephanum from S. A. Shah, M. Turi et al. SAS- 40 O, P V. kenouriense from S. A. Shah & L. Ahmad SAS- 37 Q, R V. lenifolium from S. A. Shah SAS- 44 S, T V. luridum from S. A. Shah & I. Ahmad SAS- 23 U, V V. lenifolium from N. Ali 1029 W, X V. sakesarense from I. Ahmad 27821 Y, Z V. stewartianum from R. R. Stewart 16709 AA, AB V. stocksii from B. Gul, N. Khan et al. SAS- 21 AC, AD V. subcanescens from A. Sultan, Z. Saqib et al. SAS- 52 AE, AF V. subcanescens from S. A. Shah & A. Ullah SAS- 8. Drawing by M. Saleem and S. A. Shah.

Figure 3. Illustration of corona types observed in southern Asian Vincetoxicum. The dark coloured shapes show corona lobes A Vincetoxicum arnottianum from S. A. Shah & B. Ali SAS- 4 (RAW) B V. cabulicum from W. Koelz 11764 (US) C V. cardiostephanum from S. A. Shah, M. Turi et al. SAS- 40 (RAW) D V. glaucum from W. Dudeeon & L. A. Kenoyer 56 (MO) E V. kenouriense from S. A. Shah & L. Ahmad SAS- 37 (RAW) F V. lenifolium from S. A. Shah SAS- 44 (RAW) G V. luridum from S. A. Shah & I. Ahmad SAS- 23 (RAW) H A variable specimen of V. lenifolium from N. Ali 1029 (RAW) I V. sakesarense from I. Ahmad 27821 (RAW) J V. stewartianum from R. R. Stewart 16709 (RAW) K V. stocksii from J. F. Duthie 18918 (RAW) L V. subcanescens from S. A. Shah & A. Ullah SAS- 8 (RAW). Drawing by M. Saleem and S. A. Shah.

Figure 4. Pollinaria of southern Asian Vincetoxicum A, B V. arnottianum C V. cabulicum D, E V. cardiostephanum F V. glaucum G, H V. kenouriense I, J V. lenifolium K, L V. luridum M V. lenifolium N, O V. sakesarense P V. stewartianum Q, R V. stocksii S, T V. subcanescens.

Figure 6. Geographic distribution of southern Asian Vincetoxicum. The colour of the symbols corresponds to the colour of the corolla.

Figure 14. Vincetoxicum stewartianum illustrated by M. Saleem from R. R. Stewart 16709 (RAW) A plant B adaxial surface of leaf C abaxial surface of leaf D corona.