Vincetoxicum stylesii Meve, Heiduk & Liede, 2020

Meve, Ulrich, Heiduk, Annemarie & Liede-Schumann, Sigrid, 2020, A new endemic Vincetoxicum (Apocynaceae) in the Eastern Cape, and a conspectus of the genus for South Africa, Phytotaxa 447 (3), pp. 185-194 : 188-190

Vincetoxicum stylesii Meve, Heiduk & Liede , sp. nov. ( Figs. 3 & 4 ).

Diagnosis:— Most similar to to V. tenuipedunculatum ( Schumann 1893: 144) Meve & Liede in Liede-Schumann & Meve (2018: 165) with regard to the gracile habit, thin stems and pedicels, elliptic-lanceolate, (sub)apiculate leaves, lax and few-flowered inflorescences on filiform peduncles, and delicate star-shaped flowers. However, V. stylesii is uniquely characterized by its spreading and rhomboid corona lobes (vs. transverse and oblong-ovoid in V. tenuipedunculatum ).

Type:— SOUTH AFRICA. Eastern Cape Province: Dwesa-Cwebe Nature Reserve, north side of Mbashe River , 15 Feb 2019, D. G. A Styles 5722 (holo, NU; iso, BR, BNRH, K, UBT, 2 sheets) .

Plants gracile, climbing and twining, to 2 m high. Latex clear. Root system fibrous. Shoots perennial, herbaceous (green), 1–2 mm diam., scatteredly pubescent all over when young, glabrescent, with additional line of trichomes along internodes, trichomes translucent, recurved. Leaves petiolate, tendentially heterophyllous with smaller leaves at the (flowering) short stems, petioles 3–6 mm long, filiform, scatteredly pubescent; leaf blades herbaceous, membraneous, 10–45 mm long, 3.5–12.0 mm wide, discolorous with upper side fresh green, lower side brighter green, elliptic to sublanceolate, apically acute, usually apiculate, basally obtuse to attenuate, adaxial base of lamina usually with 2 colleters, surfaces glabrous except for scattered trichomes on midribs. Synflorescences extra-axillary, one per node, occasionally branched, with peduncle 10–21 mm long, filiform, with minute, deltate bracts; inflorescences sciadiodal, lax, 2–5-flowered. Pedicels 6–12 mm long, filiform, with scattered trichomes. Flower buds conical. Calyx with scattered trichomes; sepals c. 1 mm long, triangular, acute. Flowers with faint musky scent. Corolla campanulaterotate, with short tube and spreading lobes, 7–8 mm diam., adaxially bright yellow to greenish; corolla tube c. 1 mm deep, 2.0– 2.5 mm wide, glabrous; corolla lobes c. 3.0 x 1.5 mm, triangular-lanceolate, slightly convex, horizontal to slightly ascending, adaxially scatteredly papillate. Gynostegial corona c. 0.75 mm long, 1.6 mm diam., the free staminal corona lobes c. 0.5 x 0.5 mm, fleshy, subtruncate, rhomboid in top view, spreading, slightly gibbose on upper surface and nectariferous, pale yellow to reddish. Gynostegium subsessile, fertile part of anther rectangular, c. 0.20 x 0.35 mm, bright yellow; anther wings c. 0.2 mm long, vertical, straight with adjacent anther wings parallel to one another, connective appendages suborbicular, c. 0.2 mm diam., appressed to the discoid style-head. Pollinarium: corpusculum 80 x 35 µm, elliptic; caudicles 70 x 20 µm, horizontal, subapically attached to adaxial side of the pollinia, pollinia in suberect position when attached to lateral sides of style-head before extraction, pendulous after extraction, c. 180 x 80 mm, ovoid. Fruits and seeds not seen.

Phenology:—Flowering December to February, fruiting unknown.

Distribution and Habitat:— South Africa, Eastern Cape Province, only known from Dwesa-Cwebe Nature Reserve so far ( Fig. 1 ). Gracile twiner in undergrowth of primary forests.

Etymology:—Named after David Styles (Durban, South Africa), botanist, collector and discoverer of this (and other) new seed plant species.

Conservation Status:—The Area of Occupancy (AOO) is around 60 km 2 (and thus <500 km 2), with just 2 locations known (<5); and the number of mature individuals is <250. That would already be two important prerequisites for classifying it as endangered under the B category of IUCN (2012), but since nothing is known about possible decline or fluctuations in the AOO, V. stylesii is actually better treated as “Data Deficient” (DD) according Red List of threatened species categories ( IUCN 2012).

Figures

FIGURE 1. Distribution map for Vincetoxicum stylesii (RSA, Eastern Cape; see black dots).

FIGURE 3. Vincetoxicum stylesii. A, Habit (from Styles 5722, UBT); B, Root system; C, Inflorescence (Styles 5401); D, Flower; E, Corona (and papillate corolla bases) in top view (glossiness of corona lobes due to nectar coating; from Styles 5722). Photograps by D. Styles (B-D) and A. Heiduk (E).

FIGURE 4. Vincetoxicum stylesii. A, Leaves from a long and a short shoot; A´, Leaf from a long shoot; B, Flower in top view; C, Flower from adaxial side; D, Gynostegium with corona in lateral view; E, Style-head with two pollinaria still attached (natural position after removal of anthers); F, Pollinarium. Drawn by U. Meve from Styles 5401 (A, B) and Styles 5722 (A´, C–F).