Dioscorea rupicola Kunth, 1850

Wilkin, Paul & Muasya, A. Muthama, 2015, Clarifying the Dioscorea buchananii Benth. species complex: a new potentially extinct subspecies for South Africa, PhytoKeys 48, pp. 51-72 : 60-62

Dioscorea rupicola Kunth Figure 3C, D

Dioscorea rupicola Kunth, Enum. Pl. 5: 378 (1850).

Type.

SOUTH AFRICA. No further data, plant obtained by Ecklon possibly from the Winterberg mountains cultivated in Berlin s.n., ♂ fl. 27 Jul 1836 (holotype: B†; isotype K! [K000098907!]).

Description.

Twining vine to not more than 5 m in height. Vegetative growth annual from a perennial tuber. Mature tuber apex to 4 × 4 cm, buried to 15 cm below soil surface, irregularly ridged longitudinally, corky, with an apical depression bearing shoot(s, usually 1 per year) and hard, brown, deltoid cataphylls to 15 mm long; base of tuber bearing 1-3 branches to 30 × 1- 3 cm long, corky and fissured externally and bearing wiry roots, parenchyma white, brittle (fide Archibald 1968). Indumentum absent. Stems to 4 mm in diam., left-twining, terete but longitudinally ridged, unarmed, pale green, sometimes pink, purple or brown-hued, branched above, cataphylls present towards base, to 6 × 3 mm, deltoid, apex caudate, recurved (fide Archibald 1968). Leaves alternate, blade 20-104 × 15-85 mm, ovate to narrowly so or lanceolate in outline, weakly to strongly 3- to 7-lobed around point of petiole insertion, rarely entire, juvenile plants with wholly entire leaves, usually broadly ovate to orbicular, texture chartaceous (thinner in juveniles), primary venation in shallow channels on upper surface in fresh material and lamina between secondary veins weakly bullate, shiny mid green above, paler below, drying olive green below, browner above; margins weakly undulate in fresh material, base cordate, sinus (1-)3-33 mm deep, lobes to 36 mm long, apically obtuse to rounded, apical lobe lanceolate to lanceolate-deltoid or lanceolate oblong, apex broadly acuminate with a 0.5-5 mm long narrow, caudate, thickened forerunner tip that appears channelled above, brown, veins usually 7, 3 in apical lobe with 2 per side running into basal lobe(s), sometimes a smaller vein close to the basal sinus, primary and secondary venation prominent below; petiole 10-67 mm long, ridged and with a narrow channel on upper surface, colour as stem, basal pulvinus flattened and broadly deltoid towards point of insertion onto node, especially in larger leaves, lateral nodal organs absent but in largest stems nodes swollen with a blunt projection on either side of petiole insertion onto node; axillary bulbils not present. Inflorescences 1 per axil, simple, axes angular, pale green, flowers campanulate; male inflorescences 20-86 mm long, peduncle 5-14 mm long, ca 1 mm in diam. at base, racemose, erect and bearing flowers ca 2-8 mm apart, buds oriented towards apex in very early development but at least patent to axis and usually recurved towards its base at anthesis, female inflorescences 9-82 mm long, peduncle 9-24 mm long, spicate, pendent, flowers oriented towards apex in very early development but usually patent to axis to ascending at anthesis. Flowers with 6 tepals, buds turbinate, apex acute-conical, at anthesis pedicel, tepals and torus exterior pale green to yellow-green, torus inner surface light pink to purple, possessing a light, sweet fragrance (fide Moll 1400, Archibald 1968); male flowers borne on 0.6-1.5 mm long curved, stout, obconic pedicels, floral bract 1 per flower, at pedicel base 1.0-1.7 × 0.4-0.7 mm long, ovate to narrowly so, acuminate, concolorous with pedicel and flower when fresh, paler brown than flower when dry; bracteole 1 per flower, similar, usually narrower and slightly shorter; tepal whorls virtually undifferentiated, inner slightly broader, tepals free, outer whorl 2.0-2.8 × 0.6-1.3 mm, inner whorl 2.0-3.7 × 0.8-1.5 erect to ascending, lanceolate to deltoid-lanceolate, apex acute but cucullate and appearing blunt, tepals inserted on the margin of a 1.0-2.1 mm diam. fleshy torus, when fresh externally broadly convex, internally with 3 swollen lobes forming an annulus with a central depression in flower centre, shape lost in drying but darker than tepals; stamens 3; filaments 0.35-0.7 mm long, inserted at base of each torus lobe on outer edge adjacent to outer whorl tepals, erect, weakly incurved, pale green, anthers 0.25-0.35 × 0.25-0.35 mm, very broadly oblong-orbicular, introrse, basifixed, pale yellow; pistillode ca 0.1 mm long, conical; female flowers overall shape as male, sessile, floral bract 1.0-2.0 × 0.6-1.2 mm, ovate to broadly so, acuminate, concolorous with inflorescence axis, bracteole narrower and thinner, both erect and appressed to ovary base; ovary 3.8-9.1 mm long, 3-angled, lorate to very narrowly elliptic in outline, pale green, sometimes purple-hued, apex weakly constricted, tepals 2.3-3.1 × 0.7-1.7 mm, shape and habit as male, inserted on the margin of a 1.8-2.5 mm diam. fleshy torus, when fresh forming an annulus in centre of flower bearing 3 0.1-0.7 mm long staminodia opposite outer tepals; style inserted in central depression, 0.9-1.2 mm long, styles 3, spreading, bifid, gynoecium concolorous with tepals. Capsule (18-)20-30 × 13-20 mm, pedicel reflexed and thus more or less erect at dehiscence, oblong-elliptic to obovate in outline, thick-chartaceous, base obtuse, apex rounded to truncate, dry and withered flowers persistent until relatively late in development (early April) on a ca 1.5-2 mm long stipe, pale brown with darker coppery-brown speckling, dehiscing apically at least at first. Seed 4.6-6.5 × 5.0-6.5 mm excluding wing, irregularly lenticular, dark brown, wing 10.5-18.8 × 6.7-8.3 mm, oblong to oblong-elliptic, winged all round margin though with elongated towards rounded to obtuse base and apex, pale brown, translucent with fine paler speckling.

Distribution.

South Africa, endemic to the Eastern Cape (as far west as the Winterberg) and KwaZulu Natal.

Vernacular name(s).

Cunningham 2486, a sterile specimen grown from a root bought at Umlazi Muthi market appears to be Dioscorea rupicola and has the name iMpinyampinya. The name inKwa may also be associated with this species.

Ecology.

Dioscorea rupicola grows in the margins of and clearings in forests and bush (including Leucosidea sericea woodland) and is often associated with watercourses and rocky kloofs. Archibald (1968) stated that it occurs on shady eastern and southern slopes on moist black doleritic soils in association with Podocarpus falcatus and Olea capensis in the Eastern Cape and that it is associated with and dolerite boulders. It is usually encountered from 1200 to 2100 m, but has been collected at lower altitudes in Alexandra District ( Rudatis 1269, 600 m) and Umzinto District (Strey 7052, ca 580 m) in KwaZulu Natal.

Conservation.

Dioscorea rupicola is found widely in higher elevation sites in the Eastern Cape and KwaZulu Natal. Its EOO and AOO will greatly exceed the threshold for threatened IUCN categories (20, 000 km2/2000 km2) ( IUCN 2001) and its provisional status is LC.

Uses.

None known. Like Dioscorea multiloba , data on the steroid content of this species is desirable.

Notes.

The specimens bearing labels Dioscor. 3, Ecklon & Zeyher 21.12 at TCD (♂ fl.) and LE (seen by Prain in 1916 according to a note on the Kew isotype) appear likely to have made from the plant material that was taken to Berlin and cultivated to yield the type. Alternatively it is possible that they were collected from other plants with that seed or tuber in late 1831 or early 1832. The locality 21.12 suggests that the collection was made in the Winterberg mountains in the Eastern Cape ( Glen and Germishuisen 2010). Thus these specimens are likely to represent clonotype or paratype material.

Unpublished sequence data shows that Dioscorea rupicola forms a clade with the other two species covered here. Thus the shift in androecium morphology is likely to be a recent, pollinator-driven event correlated with the erect inflorescences bearing recurved flowers with erect to ascending tepals (Fig. 3C, D).

Specimens examined.

South Africa. Eastern Cape: Winterberg Mountains, ♂ fl. late 1831 or early 1832, Ecklon & Zeyher s.n. (TCD!, LE) (see Notes above); Collected at Mt. Kemp, Keiskamma Hoek and cultivated at Irene, ♀ fl. 20 Dec 1954, Pole-Evans 4847 (K!, PRE); Fort Beaufort District, Hogsback, big dolerite cliff near top of pass facing South, ♂ & ♀ fl. 10 Dec 1961, Archibald 7557 (K!); same locality, ♂ fl. (post anthesis) & ♀ fr. 27 Apr 1962, Archibald 7560 (K!); same locality, ♂ fl. 15 Nov 1961, Archibald 7537 (PRE!); Victoria East, on pass Port Elizabeth aspect, ♂ fl. 15 Nov 1961, Archibald 7551 (K!); Victoria East, about ¼ way up pass, sterile 15 Nov 1961, Archibald 7552 (K!); Victoria East, about ¼ way up pass, ♀ fl. 10 Dec 1961, Archibald 7558 (K!); Hogsback, ♂ fl. 27 Dec 1944, Acocks 11019 (K!); Victoria East, Hogsback Natural Forest Reserve, above Swallowtail Falls, sterile 17 Apr 1955, Johnson 1273 (K!, PRE); King William’s Town District, no further data, ♂ fl. 26 Jan 1956, Comins 1425 (K!, PRE); Mountains near Ntsizwa (in umbros. Mont. Jnsiowa), ♂ fl. 28 Jan 1895, Schlechter 6443 (K!, PRE!, Z digital images!); Insizwa Forest Reserve, sterile 23 Feb 1958, Wilson & Buchner 163 (K!); Insizwa Forest Reserve, sterile seedling 23 Feb 1958, Wilson & Buchner 164 (K!); Insizwa Forest Reserve, sterile seedling 23 Feb 1958, Wilson & Buchner 165 (K!); Insizwa Forest Reserve, sterile seedling 23 Feb 1958, Wilson & Buchner 166 (K!); Insizwa Forest Reserve, sterile seedling 23 Feb 1958, Wilson & Buchner 167 (K!); Insizwa Forest Reserve, sterile 23 Feb 1958, Wilson & Buchner 16 (K!); Kokstad, Tabankulu Forest, ♂ fl. Jan 1925, Dist. Forest Officer 558 (PRE!); Prentjiesberg, Ugie "Forest Reserve", sterile 12 Nov 2000 Potgieter 392 (NU [NU0028393, 4]). (2 sterile sheets, possibly Dioscorea rupicola (28393) and Dioscorea multiloba (28394).) KwaZulu Natal: Alfred District, Weza, Ingeli (Ngeli) slopes, 1 Jan 1966, Strey 6284 (K! ♀ fl., (NU [NU0028252 digital image ♂ fl.!], PRE, UDW digital image ♂ fl.!); Alfred District, Ngeli Mountain, ♂ fl. & ♀ fl. 2 Jan 1969, Hilliard & Burtt 5758 (E, K!, NU [NU0028253 digital image!]); Weza State Forest, South boundary of Farm Diabolo, ♂ fl. 3 Dec 1989, Abbott 4583 (NH, PCE!, PRU); Griqualand East, Mount Currie, ♂ fl. Feb- Apr 1883, Tyson 468 (K!, Z digital image!); Griqualand East, Mount Currie, ♀ fr. Feb- Apr 1883, Tyson 1433 (K! Z digital image!); Kokstad, Mt. Currie slopes, ♂ fl. without date, Dist. Forest Officer 636/F.D. Herb 7215 (K!, PRE!); Polela District, Farm “Glengariff”, ♂ fl. late Jan 1981, Rennie s.n. (NU [NU0028254 digital image!]); Polela District Ndunduina Bush, Glengariff, 5 Jan 1974, Rennie 510 (NU [NU0028391 digital image!]); Sunset Farm, 2929DC, ♂ fl. buds 17 Jan 2000, Rennie 2526 (NU [NU0028259 digital image!]); Umzinto District, Ellesmere, ♂ fl. 18 Dec 1966, Strey 7052 (K!, NU [NU0028356 digital image!], UDW, possibly also at PCE (Ellesmere,? Dumisa, 19 Dec 1966)); Alexandra District, Ellesmere, ♂ fl.20 Feb 1910, Rudatis 1269 (K!); Eastern Frontier C.B.S, Botha’s Hill, ♀ fl. without date, Macowan 537 (TCD!) Weenen, old bush above ‘Lulwers’, ♂ fl. Dec 1923 Rogers 28163 (Z digital image!); York-Rietvlei road, ca 1 km South of Karkloof turnoff, ♂ fl. 17 Jan 1987, Goldblatt & Manning 8362 (MO, NU [NU0028236 digital image!], PRE!); On Road Bulwer to Underberg-SA Paper Pulp Forest, ♀ fl. & immature fr. 22 Feb 1958, Wilson & Buchner 156 (K!, 4 sheets); On Road Bulwer to Drakensberg Garden, ♂ fl. 22 Feb 1958, Wilson & Buchner 159 (K!, 3 sheets); Drakensberg, upper Umkomaas, ♂ fl. 15 Dec 1958, Werdermann & Oberdieck 1395 (B, K!); Underberg District, Cobham State Forest, Emerald Vale, ♀ fl. & immature fr. 4 Mar 1985, Hilliard & Burtt 18309 (E, NU [NU282256 digital image!]); Underberg District, Cobham State Forest, Emerald Vale, ♂ fl. 14 Jan 1985, Hilliard & Burtt 18061 (E, NU [NU282257 digital image!], PRE); Underberg District, Sunset, Upper Lurane, ♀ fl. & immature fr. 12 Jan 1980, Rennie 1095 (NU [NU0028389 digital image!]); Underberg District, Sunset, Upper Lurane Valley, ♂ fl. 12 Jan 1980, Rennie 1094 (NU [NU0028392 digital image!]); Mpendhle District, Loteni Nature Reserve, Ngondwini valley, ♂ fl.25 Dec 1978, Hilliard & Burtt 11828 (K!, NU [NU0028386 digital image!]); Impendhle District, cultivated in Pretoria, sterile Feb 1962, Roux s.n. (K!, PRE); Bergville District, Cathedral Peak area, ♂ fl. 3 Dec 1952, Killick 1812 (K!, NU [NU0028399 digital image!], PRE); Lions River District, Nhluzane, ♂ fl. 28 Oct 1976, Hilliard & Burtt 9091 (K!, NU [NU0028388 digital image!]); Lions River District, Ross, Umgeni Poort, ♂ fl. 21 Dec 1964, Moll 1400 (K!, (NU [NU0028396 digital image!], PRE); Ngotshe, collected at Ngome Forest and cultivated at Irene, ♀ fl. & immature fr. 20 Dec 1954, Pole Evans 4852 (K!, PRE); Ngotshe District, Ngome, above forest ♀ fr. 2 Apr 1977, Hilliard & Burtt 9932 (K!, NU [NU0028387 digital image!]); Louwsburg District, Ngome, ♂ fl. 14 Dec 1969, Strey 9370 (K!, NU [NU0028397 digital image!]); Vryheid District, Nhlugatshe Mt., ♂ fl. 18 Dec 1965, Hilliard & Burtt 3354 (E, NU [NU0028258 digital image!]); Drakensberg, Estcourt, Cathkin Park, ♂ fl. 22 Jan 1932, Galpin 11744 (K!, PRE); Inanda, no further data, ♂ fl. Without date, received Apr 1881, Wood 1167 (K!); Champagne Castle, ♂ fl. Jan 1955 Odhner 44 (NU [NU0028398 digital image!]); Drakensburg, Giant’s Castle, ♂ fl. 12 Jan 1949, Brunjis-Haylett 20 (NU [NU0028400 digital image!]); Giant’s Castle Game Reserve, ♂ fl. 20 Dec 1987, Cunningham 2720 (NU [NU0028345 digital image!]).