Vincetoxicum arnottianum (Wight) Wight, Icones Pl. Ind. Or. t. 1614. 1850.

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

1. Vincetoxicum arnottianum (Wight) Wight, Icones Pl. Ind. Or. t. 1614. 1850. Figs 2G-J , 3A , 4A, B , 5 , 6

Type.

India. Kashmir: 'In itinere ad Cashmere’, Royle, 21 (Holotype: K! [K000872738]).

Undershrubs, up to 100 cm tall. Stem striate, pubescent along one narrow line throughout the stem or alternating along two lines, sometimes both single and double lines found, internodes 0.5-10 cm long. Leaves usually opposite, rarely 3-4 whorled; petioles 2-13 mm long, pubescent along adaxial channel, abaxially glabrescent, rarely pubescent all around; lamina discolorous, narrowly ovate to lanceolate-ovate, 3-13 × 1-3.5 (-5) cm; apex acute to narrowly acute; base obtuse; veins visible on both sides, sometimes inconspicuous, secondary veins 8-10 (-14) on each side of midvein; both surfaces and abaxial veins glabrous, adaxial veins pubescent; margins sparsely pubescent. Inflorescences sessile, very rarely pedunculate; peduncles up to 1.5 cm long, pubescent; bracts linear with ciliate margins, ± 1 mm long; pedicels 1-5 mm long, pubescent along single or double lines, sometimes glabrous. Flowers 4.5-5.5 × 2-3 mm; sepals gradually tapering to narrowly acute or acuminate apices, up to 2 mm long, margins ciliate, sometimes pubescent on abaxial surface; calycine colleters 5 or 10, unequal in length when paired; corolla dark purple, corolla tube ca. 1 mm long, lobes twisted clockwise, bearded over the whole surface within except for the lateral margin, oblong, gradually tapering to the apex, 2.5-4 × 1-2 mm; corona deltoid-rhomboid, broader than long, 0.6-0.8 × 0.8-1 mm, reaching the bases of the staminal appendages in length or rarely equalling the gynostegium, divergent. Follicles fusiform, 4-7.5 × 0.8-1 cm, apex acuminate, surface glabrous, striations inconspicuous. Seeds reddish brown, 6-8 × 3-4.5 mm, wings up to 1 mm broad, brown dots rarely distantly present; coma up to 2 cm long.

Distribution and habitat.

Based on the number of past collections and our field observations, this is the most commonly occurring species of Vincetoxicum in southern Asia. It is strictly western Himalayan in distribution and found in India (Himachal Pradesh), Kashmir and Pakistan (Azad Jammu, Kashmir and Hazara Division). It is a deep rooted plant with a thick root stock found on open, sunny mountain slopes in association with grasses or other herbaceous flora. Its elevation ranges from 750 to 2800 m.

Phenology.

Flowering from April to September and fruiting from May to October.

Provisional conservation status.

Near threatened (Table 1 ). Vincetoxicum arnottianum is found in highly clumped and distant populations. Its populations have been mostly found in areas less than 100 m2 in size and consist of less than 100 plants.

Notes.

Vincetoxicum arnottianum has been confused with closely related entities for a long time. However, in recent studies ( Ali and Khatoon 1982; Shah et al. 2018), those entities are regarded as separate species, namely V. lenifolium (this paper), V. luridum , V. sakesarense and V. stocksii . The inter-species relationships within the V. arnottianum complex (except V. lenifolium ) were discussed in Shah et al. (2018). However, there are two associated problems that still need more clarification. Firstly, the type specimen of V. arnottianum was collected from western Himalaya, but the drawings on the herbarium sheet depict characters of a Balochistani species V. luridum , that we recently introduced as a new species in Shah et al. (2018). We hereby present our detailed observations to clarify this first problem.

Robert Wight provided two descriptions of V. arnottianum , notably in the protologue ( Wight 1834), and a revised description ( Wight 1850). In the former, he described V. arnottianum as a glabrous plant with oblong, obtuse or emarginate leaves, sessile umbels, 5-fid internally hairy corolla lobes, 5-fid corona lobes (shape not provided) equal to the gynostegium. The type designated was "In itinere ad Cashmere, Royle (K [K000872738])". The locality mentioned means "on the way to Kashmir". Kashmir (India) is part of the western Himalaya. For the revised description, Wight acquired specimens from Dr. Stocks collected from Balochistan and named them V. luridum . The name " Vincetoxicum luridum " was limited to those specimens and Stocks did not publish the species. Three specimens of that collection are housed in K, with K001235295 chosen as holotype of V. luridum ( Shah et al. 2018). Wight (1850) regarded both K000872738 and Stocks’ collections as one species as opposed to Stocks’ view. Therefore, in the revised description, Wight (1850) added the following characters: suffruticose, climbing, branches terete, leaves succulent, umbels subsessile, many-flowered, stigma apiculate. In the geographic distribution, he mentions “Beluchistan” (correct spelling is Balochistan or Baluchistan). According to our observations, these revised characters predominantly belong to the Balochistani collections. Therefore, Wight’s (1850) revised description is based on two different taxonomic entities. Balochistan is located in south-western Pakistan, not in the Himalayas, and has its own mountain ranges far away from Kashmir (see distribution map in Shah et al. (2018). Wight (1850, p. 17) acknowledged Dr. Stocks for his collections and stated: " This species was first taken up from rather imperfect specimens, whence some alterations have here been found necessary to adapt the character to the species. I am indebted to Dr. Stocks for the specimens from which the drawing and revised character were taken ". On the other hand, one of the Stocks’ specimens (K001235295) has a manuscript note in Stocks’ handwriting " figured by Wight in his Icones from my specimens as his Vincetoxicum arnottianum I doubt ". Wight used the term “climbing” in the revised description because he observed Stocks’ specimens. He did not use this term in the 1834 description. The illustration provided in 1850 depicts a somewhat climbing habit. The type of V. arnottianum K000872738 does not show a climbing habit. The term “suffruticose” and other characters of the revised description, and some floral and pollinarium drawings were provided on a label of the type specimen K000872738. These observations further indicate that the revised characters as well as the drawings including the pollinarium pertain to Stocks’ specimens (Balochistan). The illustration provided in Wight (1850) was also drawn from Stocks’ specimens and perfectly resembles the Balochistani collections, not the western Himalayan specimens.

During this study, we thoroughly examined the type specimen of V. arnottianum , K000872738, the types of V. luridum (holotype K [K001235295], isotypes: K [K001235294], [K001235296]) as well as almost all Vincetoxicum collections from western Himalaya and Balochistan. The type of V. arnottianum resembled western Himalayan specimens in its characters and differed from those of Balochistan. Furthermore, the specimens of western Himalaya do not match those of Balochistan in morphological characters and the two areas are geographically distant and climatically different. These findings led us to our decision in Shah et al. (2018) to introduce V. luridum as a new species and maintain K000872738 as the type of V. arnottianum . Our detailed morphological comparison is provided hereby.

The type K000872738 is glabrous, which is a character of V. arnottianum (western Himalayan) as also mentioned in the protologue by Wight (1834). Vincetoxicum luridum is densely hairy.

In K000872738, the inner surfaces of the corolla lobes are bearded, not pilose like in V. luridum.

In K000872738, the inflorescences are not many-flowered like those of V. luridum.

In K000872738, the corolla is dark purple as mentioned in the protologue by Wight (1834). In V. luridum, the corolla lobes are bicolored (lower half purple + upper half green). In this taxon, as well as in V. stocksii, flower color can only be correctly determined in fresh flowers.

In K000872738, the corolla lobes do not seem twisted because the flowers are immature and pressed. However, we have observed twisted corolla lobes in V. arnottianum while studying fresh flowers. In K000872738, the apex of the flowering bud is acute rather than obtuse as in V. luridum. A twisted corolla is never found in the Balochistani specimens belonging to V. luridum.

Secondly, we have observed significant morphological variation in certain populations of V. arnottianum . In these populations, plants are comparatively short (ca. 1 feet or rarely up to 2 feet), leaves are either pubescent (Fig. 2A-D ) or glabrous on both sides (Fig. 2E-H ), flower colour either purple or rarely whitish green, corolla length varies from 2 to 5 mm, corona shape is either rhomboid or deltoid-rhomboid or rarely deltoid. The geography of these populations is different from the typical V. arnottianum . They occur in Rawalpindi district (Punjab province, Pakistan) and in Malakand division (Khyber Pakhtunkhwa province, Pakistan) comprising districts Buner, Chitral, Upper Dir, Lower Dir, Malakand, Shangla and Swat. Geographically, Malakand Division represents the eastern Hindukush mountain range and borders Afghanistan in the west. The major geographic disjunction between Malakand division and the range of typical V. arnottianum (India: Himachal Pradesh, Kashmir; and Pakistan: Azad Jammu, Kashmir, and Hazara Division) is the River Indus. Therefore, in this study, we just highlight this problem and propose to identify the plants possessing the above-mentioned variations as Vincetoxicum sp. aff. arnottianum . We also recommend further detailed studies preferably including a molecular analysis using variable markers to determine whether these populations could potentially prove one or more new taxa in the purple-flowered Vincetoxicum species complex. We cite representative specimens of these populations below.

Specimens examined.

India. Masrund , Chamba State, 21 June 1917, 5000 ft., R.R. Stewart 2317 (RAW; MO); Bank of Ravi between Tiari & Siunn in dry places, Chamba State, 5000 ft., 04 July 1919, R.N. Parker s.n. (GH) .

Pakistan. Azad Jammu and Kashmir (AJK): Mountain slope near Deri Nala, 2500 ft., 06 May 2015, S.A. Shah & B. Ali SAS-4 (RAW); Mandi, Kotli, 27 April 1954, A. Rashid, E. Nasir, R.R. Stewart 27007 (RAW; BM); Kotli (Azad Kashmir), ± 2700 ft., 03 June 1977, Shahzad & Nisar 54346 & 54347 (ISL); Kotli (Azad Kashmir), 27 April 1954, J. Muhammad 16636 (ISL); Doongi (Kotli), ± 2500 ft., 01 June 1977, Shahzad & Nisar 54341 & 54342 (ISL); Mausooh (Kotli, Azad Kashmir), 30 April 1977, Shahzad & Nisar 50160 - 50162 (ISL); Nawal Nadi, Poonch, ± 2700 ft., 18 June 1977, Shehzad & Nisar 56415 & 56416 (ISL); Khohi Ratta (Kotli), 01 June 1977, Shahzad & Nisar 54344 & 54345 (ISL); Muzaffarabad, ± 3200 ft., 12 December 1975, J. Muhammad 34527 (ISL); Zamanabad (Muzaffarabad), 25 April 1978, S. Iqbal & W. Rehman 89644, 89646 & 89647 (ISL); Datta to Rara, (Muzaffarabad), 27 April 1978, S. Iqbal & W. Rehman 89650 & 89651 (ISL); Kashmir: B-8 Pahlgam, ca. 8000 ft., s.d., R.R. Stewart 5357 (K); Kashmir, Kullogam, s.d., H. Falconer 2743 (K); Kashmir, Shapiyon, 7000 ft., s.d., C.B. Clarke 28584 A, C (K); Near Shapiyon, 6000 ft., s.d., J.R. Drummond 13948 (K); Hab River banks, Lidar Valley , Kashmir, 06 June 1939, 7000 ft., J.F. Ludlow 74 (BM); Mountains above Istahal River [Kashmir], 1915, 5000 ft., Mrs. P. Decie s.n. (BM); Tanmarg [Kashmir], s.d., A.R. Naqshi 6343 (KASH); Sonamarg, Kashmir, 9200 ft., August 1928, R.R. Stewart 13101 (MO); Kashmir, s.d., H. Falconer [?], s.n. (GOET [GOET020086]); Khyber Pakhtunkhwa: Darra, mountain slope, 3940 ft., 27 September 2016, Faizan, A. Majid & S.A. Shah SAS-47 (RAW, US); Balakot ( Kaghan valley ), 6 July 1954, Ch.S. Ali s.n. (RAW); Balakot-Shogran Road, 28 June 1952, I.I. Choudhri 13511 (RAW); Abbottabad, ca. 4500 ft., 01 June 1928, R.R. Stewart 295 (KUH); Parhana [Abbotabad, KPK], 11 May 1976, Shaukat & Nisar 18472 (ISL); Parhana, Hazara, 08 May 1976, M.A Siddiqi, Shahzad, Ashraf, Manzoor, Maqsood & Dilawar 22587, 22588 & 22589 (ISL); Nari, 4 miles from Abbottabad, [KPK], 29 May 1976, M.N. Chaudhri, M.A. Siddiqi, Shehzad, Ashraf, Maqsood, Lal & Akram 22597, 22598 & - 22599 (ISL; GH[Col. No. 1122]); Bhonja [Mansehra], Hazara, 12 June 1976, Shaukat & Nisar 22600 &22601 (ISL); Balakot, Hazara, 22 April 1978, S. Iqbal & N. Ahmad 89641 (ISL); Shinkiari [Mansehra], 3500 ft., 30 May 1967, E. Nasir, Siddiqi & Zaffar 4422 (KUH) .

Representative specimens of the doubtful taxon Vincetoxicum sp. aff. arnottianum .

Pakistan. Khyber Pakhtunkhwa: Buner: Elum near Kalakhela, 860 m, 23 July 2015, S.A. Shah & F. Rahman SAS-11 (RAW); Buner: On the way from Ghazi Kot to Mah Banr, 1700 m, 26 April 2015, S.A. Shah & F. Rahman SAS-3 (RAW); Swat: Karakar, road side, 1300 m, 24 July 2015, S.A. Shah SAS-12 (RAW); Mansehra: mountain slope near Bhonja village, 5740 ft., 28 September 2016, S.A. Shah SAS-46 (RAW); Swat: Sherpalam, mountain slope under Pinus trees, 3310 ft. 10 July 2016, S.A. Shah SAS-35 (RAW); Swat: Fizaghat road side near Darul Qaza, 1050 m, 10 May 2015, S.A. Shah SAS-5 (RAW); Swat: Alam Ganj village, mountain slope, 1250 m, 20 July 2015, S.A. Shah SAS-9 (RAW); Swat: Fatehpur, mountain slope, 2500 m, 28 September 2015, S.A. Shah SAS-18 (RAW); Swat: Ghalegay, road side, 2790 ft, 07 May 2016, S.A. Shah SAS-31 (RAW); Ayubia, pipeline track, 7545 ft., 04 September 2016, R. Khan SAS-41 (RAW); Malakand: mountain slope near Butkhela bazaar, 2460 ft, 07 May 2016, S.A. Shah SAS-29 (RAW); Punjab: Rawalpindi: Punjar, road side, 2250 ft., 15 May 2016, S.A. Shah SAS-25 (RAW); Rawalpindi: Murree, Masyari, [6230 ft.], 01 August 2016, Shakeel SAS-35 (RAW!).

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 5. Field photographs of Vincetoxicum arnottianum A habit B leaves and inflorescences C flowers D follicles. Photos by S. A. Shah.

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