Vincetoxicum stocksii Ali & Khatoon., Pak. J. Bot. 14(1): 65. 1982

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

10. Vincetoxicum stocksii Ali & Khatoon., Pak. J. Bot. 14(1): 65. 1982

Type.

Pakistan. Balochistan: D-5 Near Bharat Khel on way to Zhob , erect shrub, l m. tall, 15 May 1978, S. Nazimuddin & S. Abedin 680 (Holotype: KUH!). Illustrated by Ali (1983: 36) .

Herbs to undershrubs, up to 60 (-100) cm tall. Stem longitudinally striate, pubescent along two longitudinal lines, sometimes moderately pubescent all around, internodes 1-7 cm long. Leaves opposite, decussate, lower and upper leaves smaller than the middle ones, petiolate; petioles 2-8 mm long, glabrous to sparsely pubescent, sometimes pubescent along the adaxial channel only; lamina mostly narrowly ovate to narrowly or broadly lanceolate, rarely elliptic-ovate, sparsely pubescent on both sides, 3-6 × 1-2 cm; apex acute; base mostly obtuse to sometime sub-acute; margins smooth, mostly pubescent; secondary veins 7-9 on each side of midvein, visible on both surfaces, sometimes sunken, pubescent. Inflorescences axillary, mostly sessile, often both sessile and short- to long-pedunculate inflorescences present on the same plant; peduncles up to 3 cm; bracts narrow, ca. 1 mm long, pubescent; pedicels 2-4 mm long, sparsely or densely pubescent. Flowers bicolored: calyx lobes green, and lower half of corolla lobes purple, upper half green, corona and gynostegium purple; sepals ovate or tapering into acute to narrowly acute apices, ca. 1 mm long, narrowly ovate, ca. 0.5 mm long, a few marginal and surface trichomes present, calycine colleters 5 per flower; corolla tube ca. 1 mm long, lobes oblong-ovate, ca. 2 × 1 mm, pubescent within, apex obtuse or occasionally emarginate; corona lobes subulate, ca. 1 mm long, less than 0.5 mm broad, much longer than gynostegium, apices approaching those of the opposite corona lobes, convergent; staminal appendages obtuse. Follicles narrowly ovate to fusiform, 5-9.5 × 1-1.5 cm, glabrous, inconspicuously striate, apex acuminate. Seeds 6-9 × 4-6.5 mm, dorsally dotted, lateral wings less than 1 mm broad; coma white, ca. 1.5 cm long.

Distribution and habitat.

Endemic to Zhob and Qila Saifullah districts in northeast Balochistan, Pakistan. It is found on dry stream beds made up of soil, stones and gravel. Its elevation ranges from 1300 to 2100 m.

Phenology.

Vincetoxicum stocksii flowers from April to June and fruits from June to August.

Provisional conservation status.

Vulnerable (Table 1 ). Vincetoxicum stocksii is endemic to two districts in Balochistan province, Pakistan. The populations are partially fragmented and face the threat of habitat loss especially on the dry stream beds due to rains.

Notes.

Vincetoxicum stocksii is a member of the purple-flowered group. Before its description as a new species by Ali and Khatoon (1982), it was identified as V. arnottianum . Recently, Shah et al. (2018) disintegrated V. stocksii into two species, separating from it V. luridum , an endemic of southwest Balochistan based on indumentum type on vegetative parts, corona lobes shape, pollinarium morphology and seed coat ornamentation. Vincetoxicum stocksii can be easily differentiated from V. arnottianum by the smaller pubescent leaves, the non-twisted and internally pilose corolla lobes, and the subulate corona lobes. These characters also differentiate it from V. sakesarense . The presence of both sessile and distinctly pedunculate inflorescences on the same plant is a common character shared between V. stocksii and V. lenifolium . However, green flowers, glabrous corolla lobes and smaller rhomboid corona lobes readily distinguish V. lenifolium from V. stocksii .

Specimens examined.

Pakistan. Balochistan: Northeast Balochistan: ca. 30 km from Zhob on way to Quetta , 07 July 1988, T. Ali & T. Ahmad 23361 (KUH); Janabad : ca. 33 km from Zhob on way to Qila Saifullah , 1 June 1995, T. Ali & G.R. Sarwar 2754 (KUH); ca. 20 km from Qilla Saifullah on way to Zhob ( Fort Sandeman ), 19 May 1984, S. Omer & A. Ghafoor 1640 (KUH); Murgha ( Balochistan ), 25 October 1950, A.H. Khan s.n. (RAW); Lakkaband , 21 May 1896, J.F. Duthie s.n. (RAW); Hindubagh , 7000 ft., 24 October 1969, Shariq 8318 & 8322 (PFI); Quetta, in valle 12 km. N. Murgha Kibsai, 30°48'N, 69°25'E, substr. Tonschiefer, 1600 m, s.d., K.H. Rechinger 29803 (K); Quetta: Murgha Kibsai to Fort Sandeman , ca. 30 km from Fort Sandeman , stony and sandy plain, ca. 1500 m, 19 May 1965, J. Lamond 1440 (MO); Zhob: 15 km towards Quetta, 1390 m, 17 August 2016, R. Khan, Z. Abedin, N. Khan, B. Gul SAS-21 (RAW) .