Dioscorea multiloba 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 : 55-59

Dioscorea multiloba Kunth Figure 2, 3A, B

Dioscorea multiloba Kunth, Enum. Pl. 5: 376 (1850); R.Knuth in H.G.A Engler (Ed.), Pflanzenr. 4, 43: 183 (1924).

Dioscorea diversifolia Kunth, Enum. Pl. 5: 375 (1850), non Griseb. in C.F.P.von Martius (Ed.), Fl. Bras. 3(1): 41 (1842), type only.

Dioscorea multiloba Type: South Africa. Eastern Cape: Pondoland, between Umtentu and Umzimkulu Rivers, ♂fl. & ♀ fr., Feb, year unknown, Drège 4497 (holotype: B [B_10_0278736 ♂fl. digital image!]; isotypes: G [G00018717 ♂fl. digital image!]; K [K000098903,K00098904 ♂fl. & ♀old fr.!]; OXF [OXF0004195 ♂fl. & ♀ old fr.!]; P [P00440190! ♀ fr.!]; TCD ♂fl.!).

Dioscorea natalensis R.Knuth in H.G.A Engler (ed.), Pflanzenr. 4, 43: 94 (1924), synon. nov. Type: South Africa. KwaZulu Natal: Durban [Kingsburgh], Winkle Spruit, ♂fl. 28 Feb 1912, Rudatis 1609 (holotype: B [B_10_0160974 digital image!]; isotypes K! [K000815875, K000815874] WAG [WAG0027134!]; Z [Z-000065671, Z-000065672, digital images!].

Dioscorea digitaria R.Knuth in H.G.A Engler (ed.), Pflanzenr. 4, 43: 184 (1924). Type: South Africa. KwaZulu Natal Friedenau, Umgayeflat (Alexandria), ♂fl. 1 Oct 1909, Rudatis 724 (holotype: B [B_10_0160991 digital image!]).

Type.

South Africa. KwaZulu Natal: "Probably collected in Pondoland", ♂ fl. & ♀ fr. 1840, Drège 4496 (lectotype: K! [K000098902 ♂fl. buds & ♀ fr.]; isolectotypes B [B_10_0004142 ♂fl. buds & ♀ fr., B_10_0004143 ♂fl. buds digital images!]; G [G00018675♀ fr. digital image!]; K [K000098900 ♂fl. buds & ♀ fr.!]; KIEL; OXF! [OXF00004193♀ fr.]; P [P00440187 ♀ fr., P00440188 ♂fl. buds & ♀ fr., P00440189 ♀ fr., P00440191 ♂fl. buds & ♀ fr.!], TCD ♀ fr.!).

Description.

Twining vine to ca 3 m in height, vegetative growth annual from a perennial tuber. Tuber apex only seen, ca 15 cm in diam., convex, dark brown to black, bark-like, bearing one shoot per year at central apex, according to von Teichman und Logischen et al. (1975) lobed and irregular below ground but not branched like that of Dioscorea rupicola . Indumentum absent. Stems left-twining, to ca 5 mm in diam., terete to shallowly longitudinally ridged and more so when dry, base with dense, firm processes to ca 1 mm long, dark purple-brown, becoming unarmed above and pale green to dull purple-hued. Cataphylls present towards stem base, ovate, acuminate, concolorous with stem to paler. Leaves alternate, blade 15-148 × 8-133 cm, ovate to narrowly or broadly so in outline, deeply to shallowly 3- to 7-lobed, usually lobed at base at least, blade sometimes (sub)entire in especially in leaves on terminal shoots, lobing usually concentrated in basal part of leaf close to point of petiole insertion, texture thinly to thickly chartaceous, primary venation in shallow channels on upper surface in fresh material sometimes bullate between secondary veins, primary and secondary venation prominent below, dark to mid green above, pale below, base cordate to truncate, sinus where present to 31 mm deep, lobes to 42 mm long, apically obtuse to rounded, lobe margins entire to sometimes with weak secondary lobing, apical lobe lanceolate-deltoid to broadly ovate, apex acute to obtuse, bearing a thickened, narrow, caudate forerunner tip to 7 mm long, sometimes subterminal, derived from central 3 veins of blade, pale yellow-green when fresh, brown and with margins curled inwards on upper surface when dry, primary veins 5-9, 3 in apical lobe, usually 1 per basal lobe but sometimes multiple veins per lobe in 3-lobed or entire leaves; petiole 6-54 mm long, ridged and with a narrow channel on upper surface, colour as stem, upper pulvinus sometimes paler than lower; lateral nodal organs absent and nodes not thickened but in vegetative stem leaves petiole base broader where inserted onto stem; axillary bulbils not present. Inflorescences simple, usually spicate, axes angular, pale green; male inflorescences 1-6 per axil, often 1, sometimes borne on weak axillary shoots with few to no leaves, 10-88 mm long, peduncle 2-8 mm long pendent to spreading, never erect, axis usually straight but sometimes irregularly flexuous, flowers usually solitary or rarely in clusters of 2-3, 1.2-4.6 mm apart, buds patent to axis, pendent at developing inflorescence apex only in very early development; female inflorescences 7-84 mm long, peduncle 4-10 mm long, flowers patent to axis at anthesis but ascending to erect soon thereafter. Flowers (sub)globose in bud, tepals 6, free, inserted on a saucer-shaped torus, spreading at anthesis, whorls scarcely differentiated, yellow-green to pale green, often with a darker apical mark or darker on midrib; male (sub)sessile, floral bract 1.0-1.7 × 0.4-0.6 mm, ovate to lanceolate, acuminate, concolorous with axis, bracteole similar, narrower, usually offset from bract; outer tepals 1.4-2.1 × 0.7-1.5 mm, inner 1.2-2.2 × 0.7-1.3 mm, ovate to narrowly so or deltoid, apex acute to obtuse, slightly thickened and sometimes with upcurved margins but not cucullate, inserted on margin of 1.5-2.3 mm diam. torus, thicker than tepals (but less so than in Dioscorea rupicola ) and concolorous with them, stamens 6, inserted at torus/tepal boundary at tepal base midpoint, filaments 0.35-0.7 mm long, erect but markedly incurved such that anthers are held over concave surface of torus with apices sometimes almost touching, anthers 0.3-0.5 × 0.2-0.45 mm, oblong to oblong-elliptic, basifixed, pale yellow, pistillode 0.1-0.7 mm long, variable in shape but formed by 3 centrally fused triangular ridges at 120° to each other, with a 0.35-0.6 mm diam. bowl-shaped, concave, circular to ovoid in outline, possibly nectariferous depression between each lobe demarcated by a membrane and with a denser texture than torus, pistillode apex either acute or bearing short recurved lobes; female flowers sessile, floral bract 0.9-1.6 mm long, appressed to ovary base, otherwise bract and bracteole as male; ovary 3.0-6.1 mm long, 3-angled, lorate to very narrowly elliptic in outline, pale green, apex constricted, tepals 1.5-2.5 × 0.8-1.5 mm, shape, apex and colour as male, torus 1.7-2.4 mm in diam., Tepals and torus accrescent as ovary enlarges when flowers persist and tepals sometimes becoming ascending but not erect, staminodia 6, ca 0.1 mm long, inserted at torus/tepal boundary at tepal base midpoint, style ca 1.0 mm long, erect, stout, 3-angled, broadest at base, stigmas 3, ca 0.4 × 0.9 mm, spreading, bifid, lobes broadly ovate in outline. Capsule 16-28 × 15-20(-22) mm, pedicel reflexed and thus ascending to erect at dehiscence, oblong to obovate in outline, thick-chartaceous, base obtuse to truncate, apex truncate to rounded, dry and withered flowers persistent until relatively late in development on a ca 1.0-1.7 mm long stipe, pale brown with darker coppery-brown speckling, dehiscing apically at least at first. Seed 4.6-5.0 × 3.7-5.0 mm excluding wing, lenticular, dark brown, wing 11-14 × 6.5-9.3 mm, oblong to irregularly elliptic, all round margin though with elongated towards rounded to obtuse base and apex, pale brown, translucent with fine paler speckling.

Distribution.

Endemic to South Africa (Eastern Cape to Mpumalanga) and Swaziland.

Vernacular name(s).

The only vernacular name known is wild yam.

Ecology.

Dioscorea multiloba occurs in a range of habitats but is principally associated with forest and bush margins and associated grasslands on a range of sandy and loamy substrates. In the northern part of its range it often appears to occur in swampy habitat. It is found at altitudes from close to sea level to 800 m in KwaZulu Natal. At the edges of its range the specimen from Swaziland (Compton 26691) was collected at ca 4000' (1200 m) and Flanagan 2717 from the Eastern Cape 4500' (1400 m).

Conservation.

Dioscorea multiloba is widespread in lowland KwaZulu Natal, and its distribution extends into the Eastern Cape, Mpumalanga and Swaziland. Thus 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. This status is also given by the SANBI red list programme (under Dioscorea diversifolia Griseb.)

Uses.

None known. Data on the steroid content of this species is desirable. Codd (1960) states that only three South African species contain diosgenin but the data on which this is based are not presented.

Notes.

Kunth cites male and female syntypes as follows “Drège, Herb. Cap. no. 4495. ex parte. v.s. in Herb. Luc. and Drège, Herb. Cap. No 4496. ex parte. v.s in Herb. Luc." Herb. Luc. appears to be an abbreviation for Herbarium Lucae, which formed part of the KIEL herbarium. Kunth specified that 4495 was male and 4496 female. However, there is both male and female material at K under 4496. In contrast, a single sheet in B (B_10_0004142) has fragments of both male and female plants under both collection numbers. P has female material under 4495 (P00440190) and male material under 4496 (P00440188) among 5 duplicates of both numbers. Given this confusion and the number of duplicates in European herbaria it was decided to lectotypify the species using K000098902, the most complete and representative specimen available.

The only specimen cited in the protologue of Dioscorea diversifolia Kunth, a later homonym of Dioscorea diversifolia Griseb., was Drège 4497. The material under this number at TCD appears to represent two different male plants of Dioscorea multiloba , with the left and bottom fragments possessing flexuous inflorescences and the right a straight inflorescence. The K and OXF material is different, with entire leaves, male flowers in bud and the previous season’s fruit. K has 2 very similar sheets from both Hooker and Bentham’s herbaria.

Specimens examined.

South Africa. Eastern Cape: Komga, near Kei Mouth, ♂ fl. Jan 1890, Flanagan 442 (K!, PRE); Engcoba (Ngcobo) Mountain, ♀ immature fr. Jan 1896, Flanagan 2717 (PRE!); Mquanduli, Coffee Bay, ♂ fl. 4 Mar 1953, Theron 1505 (PRE!); Pondoland, between Umtentu River and Umzinkulu River, ♂ fl.buds & old fr. Feb unknown year, Drège 4497 (K!, OXF!, TCD!). KwaZulu Natal: Port Shepstone, Mgayi, 30°25'S, 30°30'E, ♂ fl. 27 Jan 1968, Ward 6339 (NU [NU0028305], UDW); Port Shepstone, Mgayi, " 30°25'S, 30°25'E ", ♀ immature fr. 27 Jan 1968, Ward 6340 (K!, NU [NU0028304 digital image!], PRE, UDW digital image!); Inanda, ♀ fl. & immature fr. Jan?1879, Medley Wood 329 (K, 2 sheets!); Port Shepstone, Umtamvuna Nature Reserve, Beacon Hill, 31°00'33"S, 30°10'55"E, ♀ fl. & immature fr. 9 Dec 2010, Abbott 9287 (PCE!, PRU!); Port Shepstone, Umtamvuna Nature Reserve, Beacon Hill, 31°00'33"S, 30°10'55"E, ♂ fl. 9 Dec 2010, Abbott 9288 (PCE!, PRU!); Inanda, ♂ fl. Jan.?1880, Medley Wood 825 (K!); Inanda, Groenberg, ♂ fl. Mar?1880, Medley Wood 892 (K!); Lions River District, collected at Karkloof 11 July 1952 and cultivated at Irene, ♀ immature fr. 20 Dec 1954, Pole-Evans 4862 (K!, PRE); Durban, Umbilo Waterfall, ♂ fl. received Feb 1883 Rehmann 8155 (K!); Port Natal, ♂ fl. & ♀ fr. without date, Gueinzius s.n. (K!; TCD!); Port Natal,?Umgena, ♂ fl. without date, Gerrard & McKen 1920 (TCD!); Fort Bowker, ♂ fl. & ♀ fr. without date, Bowker 575 (TCD!); Kaffraria, Tsomo (?), ♂ fl.. without date, Bowker 861 (TCD!); Fort Bowker ♂ fl. without date, Bowker 627 (TCD!); Natal, no further data, ♂ fl. without date, Gerrard & McKen 36 (TCD!); Port Natal, ♂ fl. without date, Sanderson 5 (TCD!); Durban District, Umbogintwini, above lagoon, st. 10 May 1964, Ward 4976 (NU [NU0028355 digital image!]); Pietermaritzburg District, Isipingo Flats, 29°59'S, 30°56'E ♂ fl. 1 May 1971, Ward 6992 (NU [NU0028390 digital image!], UDW digital image!); Lower Umfolozi District, Hluhluwe Game Reserve, ♂ fl. 24 Jan 1949, Ward 665 (NU [NU0028255, 0028351 digital image!]); Hlabisa District, Hluhluwe Game Reserve, ♂ fl. 16 Jan 1954, Ward 2073 (K!, NU [NU0028352 digital image!], PRE); Hlabisa District, Hluhluwe Game Reserve, ♂ fl. 6 Mar 1957, Ward 3076 (K!, (NU [NU0028353, 0028354 digital images!], PRE); Mtubatuba District, Hlabisa, Park Ridge Farm, ♀ fr. 11 May 1968, Harrison 498 (PRE!); Maputaland, Kosi Bay area near Catholic Mission, sterile 20 Mar 1965, Vahrmeijer 482 (K!, PRE); Maputaland, 3 miles from Maputa on road to Olibotini, ♂ fl.23 Mar 1965, Vahrmeijer 540 (K!, PRE); KZN, No further data, ♂ fl. received Jul 1965, Gerrard 772 (K!); ♂ fl. received Jul 1965 & Mar 1872, Gerrard 1920 (K!); KZN, Locality illegible, ♂ fl. 1862, Cooper 3244 (K!). Mpumalanga: Pilgrims Rest District, collected at Mac Mac 19 Aug 1952 and cultivated at Irene, ♂ fl. 20 Dec 1954, Pole-Evans 4846 (K!, 2 sheets, PRE); Pilgrims Rest District, collected at Mac Mac and cultivated at Irene, ♂ fl. 14 Apr 1955, Pole-Evans 4861 (K!, 2 sheets, PRE). Swaziland: Mankaina District, ♂ fl. 3 Feb 1958, Compton 27492 (K!, PRE); Mbabane District, Ukutula, ♂ fl. 21 Feb 1957, Compton 26691 (K!, PRE).