Vincetoxicum glaucum (Wall. ex Wight) Rech. f., Fl. Iranica 73: 13. 1970

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

4. Vincetoxicum glaucum (Wall. ex Wight) Rech. f., Fl. Iranica 73: 13. 1970 Figs 3D , 4F , 7

Cynanchum glaucum Wall. ex Wight, Contr. Bot. India: 58. 1834. Vincetoxicum hirundinaria subsp. glaucum (Wall. ex Wight) H. Hara, Enum. Fl. Pl. Nepal 3: 89. 1982.

Type.

Nepal. Chandaghir , 5 May 1821, N. Wallich 133 [cat. #. 8229A] (lectotype: designated by Hara (1982), pointing generally to the set of syntypes: Asclep 133 and cat. # 8229A, specimen not chosen from syntypes); lectotype (designated here: K online [K000894587]; isolectotypes K online [K001129297, K000894586]; E online [E00179664, E00179665]) .

Undershrubs, up to 40 cm tall. Stem striate, pubescent all around, internodes 1-6.8 cm long. Leaves petiolate; petioles 3-11 mm long, pubescent all around; lamina different shaped: narrowly ovate, oblong-ovate, elliptic ovate, lanceolate-ovate, 4-9.2 × 1.3-3.8 cm; margins smooth; apex acute to obtuse or sometimes mucronulate; base round or cuneate; veins visible on both surfaces, secondary veins 8-12 on each side of midvein; adaxial surface sub-glabrous, adaxial veins densely pubescent; abaxial surface glabrous to sub-glabrous, abaxial veins especially midrib pubescent; margins pubescent. Inflorescences sessile; bracts linear, ciliate; sepals tapering to acute apices, 1.5 mm long with ciliate margins; pedicels 1-3 mm long, pubescent; calycine colleters 5, exceeding the corolla tube in length; corolla green, not twisted, corolla tube 1 mm long, lobes tapering to pointed apex, 2 × 1 mm, bearded within; corona lobes longer than broad, 1 × 0.8 mm, exceeding the length of the gynostegium, base narrow, apex broad, toothed, divergent; staminal appendages obtuse; pollinaria deeply embedded in the gynostegium. Follicles and seeds not seen.

Distribution and habitat.

Endemic to eastern Himalayas including India and Nepal and occurring at an elevation of over 2000 m. Herbarium label on W. Dudgeon & L.A. Kenoyer 56 (MO) indicates its habitat to be open grassy places.

Phenology.

Flowering from May to June and fruiting from July to October.

Provisional conservation status.

Data Deficient (Table 1 ). Vincetoxicum glaucum is collected from a few localities in the eastern Himalayas (India and Nepal). We did not collect or observe its populations in natural habitats. Herbarium labels do not provide significant information about its populations. Therefore, it is declared as data deficient.

Notes.

Vincetoxicum glaucum was first described as Cynanchum glaucum Wight but soon regarded as V. canescens by Decaisne (1844), a treatment which Boissier (1879) also adopted. Hooker (1883) reinstated the original name C. glaucum . Rechinger (1970) recognized V. glaucum in a broader sense and lumped with it another Afghani species, V. cabulicum Bornm. Hara et al. (1982) regarded Rechinger’s V. glaucum as a synonym of V. hirundinaria subsp. glaucum (Wall. ex Wight) H. Hara. While writing the genus Vincetoxicum for the flora of Pakistan, Ali and Khatoon (1982) lumped Rechinger’s V. glaucum with V. canescens . In the present treatment, we recognize three different species in this long misunderstood species complex, namely V. cabulicum (endemic to northern Afghanistan), V. glaucum (endemic to India and Nepal) and V. subcanescens sp.nov. (endemic to Pakistan, Kashmir and Tibet), whereas V. canescens , a species long regarded as a member of this complex, is endemic to the eastern Mediterranean region and does not occur in southern Asia (also see notes below V. subcanescens ).

Wight (1834) cited Wallich’s collection Asclep. # 133 (Cat. # 8229A) as C. glaucum (corresponding to the typical variety latifolium, denoted by “α” in the protologue), Asclep. # 132 as variety oblongifolium (denoted by “β” in the protologue), and Asclep. # 134 and Cat. # 1554 as variety lanceolatum (denoted by “γ” in the protologue). He did not designate a holotype for C. glaucum , hence the specimens cited in the protologue and their duplicates were the syntypes for the respective varieties. Later on, Hara (1982) lectotypified C. glaucum by designating Wallich’s Asclep. # 133 (Cat. # 8229A). This collection has at least five duplicates (syntypes) housed by K [K000894587, K001129297, K000894586] and E [E00179664, E00179665]). Possibly, Hara considered Asclep. # 133 a single specimen and did not choose a specimen as lectotype from the duplicates (syntypes). In spite of Hara’s attempt, the lectotype is still unknown among the syntypes. Therefore, it is necessary to choose a specimen from the five duplicates (syntypes) of Wallich’s Asclep. # 133 (Cat. # 8229A). Among them, K000894587 is chosen here as the lectotype of C. glaucum . The remaining syntypes become isolectotypes. We could not get specimen loans and examine the collections Asclep. # 132 & 134 and Cat. # 1554 that belong to the remaining two varieties of C. glaucum . Therefore, we recommend a revision for these varieties. It is also notable that there is no mention of these varieties in the post-protologue literature.

Specimens examined.

India. Uttarakhand: Landour , open grassy places, 7000 ft, 24 May 1920, W. Dudgeon & L.A. Kenoyer 56 (MO [MO-2321710]); Nepal, s.d., N. Wallich cat. # 8229A (K [K001129296]); Kumaon / Tranquebar, India, s.d., N. Wallich cat. # 8229B (K [K001129299]) .

Figures

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 7. Geographic distribution of Vincetoxicum cabulicum, V. glaucum and V. subcanescens.