Clarifying the Dioscorea buchananii Benth. species complex: a new potentially extinct subspecies for South Africa

Abstract The Dioscorea buchananii complex is shown to comprise three species, one of which is divided into two subspecies, based on morphological data. Two species, Dioscorea rupicola Kunth and Dioscorea multiloba Kunth, are endemic or subendemic to South Africa and of widespread occurrence in KwaZulu Natal. They differ markedly from each other in inflorescence and floral morphology and appear to be ecologically differentiated. The third species, Dioscorea buchananii Benth., is primarily found in southeastern tropical Africa, but a small number of specimens collected in South Africa in the late 19th and early 20th centuries are placed in an endemic subspecies, Dioscorea buchananii subsp. undatiloba (Baker) Wilkin. The latter taxon is a high priority in terms of rediscovery and conservation. Keys, descriptions, supporting information and illustrations are provided and made available online through eMonocot biodiversity informatics tools. Three nomenclatural acts are undertaken: two names are placed in synonymy and a new combination made.


Introduction
Th e Dioscorea buchananii Benth. group of species fi rst came to the attention of science through the publication of three species with palmately lobed leaves from South Africa that had been collected by some of the early botanical explorers of the Cape: D. diversifolia Kunth, D. multiloba Kunth and D. rupicola Kunth (Kunth 1850). Th e fi rst of those names was unfortunately a homonym of D. diversifolia Griseb., a Brazilian species for which a Sellow collection was cited (Grisebach 1842), although Kunth linked his name to Drège 4497 from the Cape. Two specimens of D. multiloba were cited by Kunth, Drège 4495 and 4496; both it and D. diversifolia were grouped as Cape taxa within one of Kunth's species groups based on fl oral morphological characters. Dioscorea rupicola, which was based on a plant cultivated in Berlin from material that had been received from Ecklon in South Africa, was treated separately, perhaps because it had 3, not 6 stamens unlike all its relatives. Baker (1897) recognised all 3 species described by Kunth and added a fourth, Dioscorea undatiloba Baker that he had described a few years earlier (Baker 1889) with pedicellate fl owers and "repand-pinnatifi d" central leaf lobes. Th ey were separated in the key in the Flora Capensis treatment through pedicel presence or absence, stamen number and leaf shape. A further taxon, D. junodii Burtt-Davy from Shilouvane in what is now Limpopo province was described by Burtt-Davy (1924). It was said to diff er from D. rupicola in possessing racemose male infl orescences with 6 stamens per fl ower and in its leaf shape. D. junodii was placed in synonymy with D. sylvatica Ecklon by Govaerts and Wilkin (2015). In tropical Africa, Dioscorea buchananii Benth. was described by Bentham (1882) based on a specimen from what is now Malawi with entire leaves and large fl owers in a dense, short infl orescence. Bentham did not suggest any affi nities for the species. Knuth (1924) was the fi rst taxonomist to formally group these species into an infrageneric taxon, Dioscorea sect. Rhacodophyllum Uline ex R.Knuth, following their placement as "Eudioscoreae capenses" by Uline (1897). He also described a further species, D. digitaria R.Knuth (Knuth 1924), based on a Rudatis specimen from Friedenau in what is now lowland coastal KwaZulu Natal. Th e Pfl anzenreich account (Knuth 1924) stated that it diff ered in its narrow, acute central leaf lobe and shorter male infl orescence. Knuth's key to D. sect. Rhacodophyllum is based on similar characters to those used by Baker. A further new species, D. natalensis R.Knuth was placed in separate section containing South African species with entire leaves (Knuth 1924), but its infl orescence and fl oral morphology unequivocally link it to the D. rupicola group. Th e Pfl anzenreich treatment also noted that a newly described variety of D. buchananii with palmately lobed leaves, var. ukamensis Uline ex R. Knuth linked D. buchananii to D. undatiloba and that perhaps those two species would be better combined. Knuth was the last taxonomist to study both the tropical and South African taxa of the D. rupicola species group. Archibald (1968) covered only Eastern Cape specimens and populations of D. rupicola in her account of Cape Dioscorea. Von Teichman (1975) surveyed all the species of Dioscorea in South Africa. She lists D. rupicola, D. undatiloba and D. diversi-folia though not D. multiloba. Her paper also reports a personal communication from Codd that a preliminary investigation into the taxonomy of the three species indicated that they represented a single taxon. Simultaneously in tropical Africa, Milne-Redhead (1975) sank var. ukamensis into D. buchananii with two later heterotypic names, D. mildbraediana R. Knuth and D. rhacodes R.Knuth. He stated that "the plentiful material now available shows that no taxonomic value can be placed on the leaf shape and degree of lobing". Wilkin (2001;2009) used the same broader taxon concept as Milne-Redhead but did not consider the species in South Africa except to highlight the fl oral diff erences between D. buchananii and D. rupicola.
Th e taxa of the D. buchananii complex share perennial, subterranean tubers, lefttwining habit, a tendency to possess palmately lobed leaves (but with entire leaves in some to many populations), relatively short spicate to racemose infl orescences, paired fl oral bracts and fl owers with well-developed receptacles and seeds that are winged all round the margin but with a wing that is longer than wide (often oblong-elliptic). Th e comments reported above by Knuth and von Teichman suggested that there are fewer morphological entities than species currently recognised; Govaerts and Wilkin (2015) listed D. multiloba, D. natalensis, D. rupicola, D. undatiloba and D. buchananii as accepted species names. Th us the morphology of all the taxa listed above was studied in more detail to test this hypothesis, focussing on specimens from South Africa but including data on D. buchananii from throughout its geographical and morphological ranges obtained for Wilkin (2001Wilkin ( , 2009.

Materials and methods
Th e results and revised classifi cation presented below are based on study of specimens at the following herbaria B (images), BOL, BM, K, P, PCE, PRE, NU (images) OXF, TCD and WAG and for D. buchananii COI, LISC, LMU, MAL and SRGH and include character data previously published in Wilkin (2001Wilkin ( , 2009 for D. buchananii. Th e characters given in the descriptions were scored or measured using the naked eye, a dial caliper or a dissecting microscope with a graduated eyepiece. Leaf lobe lengths were made along the central vein from level with the base of the adjacent sinus to the lobe apex. Th e research undertaken was part of the eMonocot project and the nomenclatural and descriptive content and images form part of the Dioscoreaceae scratchpad (http:// dioscoreaceae.e-monocot.org) and hence the eMonocot portal (http://e-monocot.org/).

Results and discussion
Floral morphology indicates that there are three taxonomic entities in the D. buchananii species complex, not one as reported in von Teichman et al. (1975). Th e most easily distinguished (see Table 1) has 3 stamens in its male fl owers (rather than 6), male fl owers that are pendent on an erect axis via recurved 0.6-1.5 mm long pedicels and erect to   ascending yellow-green tepals with cucullate (rather than fl at) apices in both male and female fl owers. Th is corresponds to the type of D. rupicola and is usually encountered at altitudes between 2100 and 1200 m in the Eastern Cape and KwaZulu Natal. A second taxon has patent, (sub)sessile male fl owers with spreading pale green tepals in both sexes. Th e earliest applicable name is D. multiloba. Th e types of Dioscorea digitaria and D. natalensis are lobed and entire-leafed forms of this species respectively. It is largely allopatric with D. rupicola, occurring below 800m in KwaZulu Natal and rarely at higher altitudes towards the edges of its range. Th e fi nal entity has patent pale green or greenyellow to purple-, pink-or bronze-hued male fl owers on pedicels at least 1.7 mm long. It also diff ers from D. multiloba in its male and female tepal and torus dimensions (Table 1), albeit that female specimens with fl owers at anthesis are few in number. Th is is D. buchananii, which has a wide ecological range in southern tropical Africa. During the study, six specimens from South Africa were encountered that possessed infl orescence and fl oral morphology similar to that of D. buchananii but whose leaves had at least a degree of secondary (pinnatifi d) marginal lobing, especially on the central primary lobe ( Figure 1A, H). Th is has not previously been recorded for the species. Milne-Redhead (1975) showed that both entire and palmately lobed leaves were found in D. buchananii and the collections made since 1975 confi rm this hypothesis and support reducing D. buchananii var. ukamensis to synonymy. Th e secondary lobing, in combination with the observation that infl orescence and fl oral dimensions in the six specimens overlap with those of D. buchananii (Table 1), but are in the lower part of its ranges of variation, suggest that South Africa has a distinct subspecies of D. buchananii that corresponds with the types of both D. undatiloba and D. junodii. Th e former is the earlier name so D. buchananii subsp. undatiloba (Baker) Wilkin is applicable. A further specimen, Pole Evans 4954 collected from Ixopo in KwaZulu Natal but fl owered in cultivation, was tentatively linked to D. multiloba due to the absence of secondary leaf lobing, a pendent infl orescence, fl owers with spreading tepals and incurved fi laments over three depressions in the centre of the torus. However, the presence of short pedicels and the tepal and torus dimensions suggest potential introgression with D. buchananii subsp. undatiloba. Th e two taxa are sympatric in KwaZulu Natal. In both this and the case above, an extensively sampled population-based study is needed using molecular marker data. Description. Twining vine to 10 m in height, vegetative growth annual, usually 1 shoot per year from apex of perennial, woody tuber, to ca 20 cm in diam., usually globose to ovoid, sometimes elongate or irregular, shape varying perhaps based on rockiness of substrate, externally dark grey to brown, fi ssured, bark-like. Indumentum absent. Stems left-twining, to 5 mm in diam., terete to shallowly longitudinally ridged, more so when dry, unarmed from base, green or purple-hued, herbaceous, cataphylls not seen. Leaves alternate, blade variable, 2.8-13.5 × 1.1-14.7 cm, entire or with 3, 5 or 7 shallow to deep lobes, ovate to broadly so, veins 7(-9), primary venation in shallow channels on upper surface in fresh material, primary and secondary venation prominent below, base cordate, with a shallow to deep basal sinus, rarely truncate, texture chartaceous, where lobes present central lobe to 116 mm long, lateral lobes to 35 mm long, lobes usually found primarily in vegetative stem leaves with reproductive stem leaves more weakly lobed to entire, rarely consistently lobed to shoot apices, lobes inserted from around mid-point to point of petiole insertion, lobe margins entire to (rarely) weakly undulate or in some leaves lobed to stem apices with weak to strong irregularly pinnate secondary lobing, blade or central lobe apex acute to triangularly short-acuminate, rarely obtuse or truncate, bearing a 1.5-10 mm long, thickened, very narrowly triangular, brown forerunner tip fed by the 3 central veins of blade; petiole 0.6-6.3 cm long, ridged like stem and with a narrow channel on upper surface, colour as stem, pulvinii sometimes paler or purple-hued; lateral nodal organs absent but petiole base broader where inserted onto stem, axillary bulbils absent. Infl orescences simple, usually 1 per axil, axes straight, angular, pale green or purple or brown-hued; male 1.6-7 cm long, peduncle 2-11 mm long, racemose, pendent to spreading, usually dense with fl owers 0.3-4.1 mm apart and solitary or rarely in cymules of 2-3 fl owers, on a 1.7-5.0 mm long pedicel that is angular and slightly broader towards apex, buds patent to axis, pendent at developing infl orescence apex only in very early development; female infl orescence 9-77 mm long, accrescent to ca 30 cm long in fruit, peduncle 12-20 mm long, spicate, pendent, lax, fl owers subpendent only at the earliest stages of development, patent to axis at anthesis but ascending to erect soon thereafter. Flowers turbinate in bud, tepals 6, free, inserted on margin of a saucer-shaped, weakly thickened torus, spreading at anthesis, sometimes ascending thereafter, whorls scarcely diff erentiated, 3-veined, brown, green, olive or bronze, sometimes with a pink or yellow hue or mottled; male fl ower with fl oral bract and bracteole sheathing pedicel base, bract 1.6-2.6 mm long, ovate, long-acuminate, membranous, bracteole similar, narrower, usually off set from bract; outer tepals 2.5-4.7 × 1.1-2.3 mm, inner tepals 2.7-4.5 × 1.3-2.3 mm, narrowly ovate to lanceolate or triangular, chartaceous, apex acute to short-acuminate, fl at; fi laments 0.6-1.8 mm long, erect but incurved over 2.3 -5 mm diam. torus, anthers 0.5-1.2 × 0.4-0.8 mm, introrse; pistillode to ca 0.1 mm high, 3 centrally fused triangular ridges at 120° to each other in fl at central part of concave torus; female fl ower with fl oral bract and bracteole sheathing ovary base, bract 1.6-2.4 mm long, ovate, longacuminate, membranous, bracteole similar, narrower, usually off set from bract; ovary 5-10 mm long, 3-angled, lorate to very narrowly elliptic in outline, colour as axis, apex constricted; outer tepals 2.9-4.5 × 0.8-1.9 mm, inner tepals 2.9-4.4 × 0.9-2 mm, more or less erect, narrowly ovate to lanceolate, apex acute to short-acuminate, fl at, each tepal with 0.2-0.7 mm long basal staminode inserted at the boundary with the torus at the tepal base midpoint, usually fl eshy and ovoid but sometimes substaminiform; torus 2.5-4.5 mm in diam. both tepals and torus accrescent as ovary enlarges; style 1.8-3.2 mm long, erect, divided into 3 spreading branches towards apex, stigmas bifi d, oblong to clavate. Capsule 2.2-3 × (1.8-)2-3.2 cm, pedicel refl exed and thus ascending to erect at dehiscence, lobes obovate to oblong-obovate in outline, thick-chartaceous, base and apex usually truncate, dry and withered fl owers persistent until relatively late in development on a ca 1.2-2.0 mm long stipe, light brown with chestnut-brown to coppery brown mottling, dehiscing apically at least at fi rst. Seed 2.5-4 × 3-4 mm, irregularly lenticular, dark brown wing 1-2 × 0.7-1.3 cm, broadly oblong-elliptic to rotund to irregularly so, wing extending all around seed margin although elongated towards rounded to obtuse base and apex, pale brown, translucent with fi ne paler speckling.

Dioscorea buchananii subsp. buchananii
Description. Leaves entire to moderately 3, 5 or 7-lobed at stem base and on vegetative stems but then less strongly lobed to entire on reproductive shoots, lobe margins at most weakly undulate; where lobed central lobe usually the largest, maximum length as in species as a whole, broadly ovate to lanceolate or deltoid, lateral lobes oblong to rounded. Male fl ower pedicel, tepal and torus dimensions as in species as a whole.
Distribution. Tanzania and Southern and Eastern Congo (Kinshasa) to southern Mozambique, Zimbabwe and Angola.
Vernacular name(s). See Wilkin (2001Wilkin ( , 2009. Ecology. Frequently associated with rocky habitats, often in Brachystegia woodland, but also on termitaria, in riverine forest and near mangrove swamps, on limestone and granite substrates; sea level to 1600 m (Wilkin 2001(Wilkin , 2009. Conservation. Th e broad southeastern African distribution of this species indicates that 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. Specimens examined. Representative specimens are cited in Milne-Redhead (1975) and Wilkin (2001Wilkin ( , 2009  Description. Leaves consistently moderately to deeply 3, 5 or 7-lobed from stem bases to apices, with irregular, pinnate secondary lobing present on central lobe at least; central lobe to 50 mm long, lanceolate to elliptic or rhomboid, lateral lobes to 33 mm long, oblong to narrowly so, central lobe largest to lobes more or less equal in length and width. Male fl owers on 1.7-3.7 mm long pedicels, tepals 2.3-3.7 × 1.0-2.2 mm, torus (1.5-)1.9-3.4 mm in diam.
Distribution. Endemic to South Africa in Limpopo and KwaZulu Natal provinces. Th e Limpopo specimens are from localities relatively close to those of the type subspecies in Gaza province of Mozambique.
Vernacular name(s). Not known. Ecology. Ca. 50 to 600 m altitude in KwaZulu Natal, and 700 to 1000 m in Limpopo. Associated geology, soils and vegetation unknown.
Conservation. Dioscorea buchananii subsp. undatiloba has not been recorded since 1921 in either Limpopo or KwaZulu Natal and is known from only six specimens. However, pending urgently needed searches to fi nd extant populations in Limpopo, KwaZulu Natal and the intervening areas and further research on the relationships between those populations, the most appropriate provisional conservation status assessment is DD. It is conceivable that this taxon is already extinct in part or all of its range, especially extensively developed lowland KwaZulu Natal.
Uses. None known Notes. Th e specimen labelled Junod 1416 at PRE [PRE0093186-0] is male fl owering material of D. sylvatica Ecklon. Th is explains the placement of D. junodii in the synonymy of that species in Govaerts and Wilkin (2015). However, Burtt Davy would have examined and described the K sheet cited above, hence its holotype status and synonymy under Dioscorea buchananii subsp. undatiloba. No specimen of Junod 1416 appears to be preserved at G or Z based on their online databases.  Figure 2, 3A 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 D. 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, fi rm 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. Infl orescences simple, usually spicate, axes angular, pale green; male infl orescences 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 fl exuous, fl owers usually solitary or rarely in clusters of 2-3, 1.2-4.6 mm apart, buds patent to axis, pendent at developing infl orescence apex only in very early development; female infl orescences 7-84 mm long, peduncle 4-10 mm long, fl owers 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 diff erentiated, yellow-green to pale green, often with a darker apical mark or darker on midrib; male (sub)sessile, fl oral bract 1.0-1.7 × 0.4-0.6 mm, ovate to lanceolate, acuminate, concolorous with axis, bracteole similar, narrower, usually off set 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 D. rupicola) and concolorous with them, stamens 6, inserted at torus/tepal boundary at tepal base midpoint, fi laments 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, basifi xed, 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 fl owers sessile, fl oral 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 fl owers 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, bifi d, lobes broadly ovate in outline. Capsule 16-28 × 15-20(-22) mm, pedicel refl exed 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 fl owers 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 fi rst. 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 fi ne paler speckling.

Dioscorea multiloba Kunth
Distribution. Endemic to South Africa (Eastern Cape to Mpumalanga) and Swaziland. Vernacular name(s). Th e 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. Th us 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. Th is status is also given by the SANBI red list programme (under D. 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 specifi ed 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.
Th e only specimen cited in the protologue of Dioscorea diversifolia Kunth, a later homonym of D. diversifolia Griseb., was Drège 4497. Th e material under this number at TCD appears to represent two diff erent male plants of D. multiloba, with the left and bottom fragments possessing fl exuous infl orescences and the right a straight infl orescence. Th e K and OXF material is diff erent, with entire leaves, male fl owers in bud and the previous season's fruit. K has 2 very similar sheets from both Hooker and Bentham's herbaria.  Figure 3C, D Dioscorea rupicola Kunth, Enum. Pl. 5: 378 (1850). 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 fi ssured externally and bearing wiry roots, parenchyma white, brittle (fi de 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 (fi de 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 fl attened 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. Infl orescences 1 per axil, simple, axes angular, pale green, fl owers campanulate; male infl orescences 20-86 mm long, peduncle 5-14 mm long, ca 1 mm in diam. at base, racemose, erect and bearing fl owers 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 infl orescences 9-82 mm long, peduncle 9-24 mm long, spicate, pendent, fl owers 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 (fi de Moll 1400, Archibald 1968); male fl owers borne on 0.6-1.5 mm long curved, stout, obconic pedicels, fl oral bract 1 per fl ower, at pedicel base 1.0-1.7 × 0.4-0.7 mm long, ovate to narrowly so, acuminate, concolorous with pedicel and fl ower when fresh, paler brown than fl ower when dry; bracteole 1 per fl ower, similar, usually narrower and slightly shorter; tepal whorls virtually undiff erentiated, 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. fl eshy torus, when fresh externally broadly convex, internally with 3 swollen lobes forming an annulus with a central depression in fl ower centre, shape lost in drying but darker than tepals; stamens 3; fi laments 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, basifi xed, pale yellow; pistillode ca 0.1 mm long, conical; female fl owers overall shape as male, sessile, fl oral bract 1.0-2.0 × 0.6-1.2 mm, ovate to broadly so, acuminate, concolorous with infl orescence 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. fl eshy torus, when fresh forming an annulus in centre of fl ower 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, bifi d, gynoecium concolorous with tepals. Capsule (18-)20-30 × 13-20 mm, pedicel refl exed 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 fl owers 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 fi rst. 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 fi ne paler speckling.

Dioscorea rupicola Kunth
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 D. rupicola and has the name iMpinyampinya. Th e name inKwa may also be associated with this species.
Ecology. D. 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. D. 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 D. multiloba, data on the steroid content of this species is desirable.
Notes. Th e 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. Th e locality 21.12 suggests that the collection was made in the Winterberg mountains in the Eastern Cape (Glen and Germishuisen 2010). Th us these specimens are likely to represent clonotype or paratype material.
Unpublished sequence data shows that D. rupicola forms a clade with the other two species covered here. Th us the shift in androecium morphology is likely to be a recent, pollinator-driven event correlated with the erect infl orescences bearing recurved fl owers with erect to ascending tepals (Fig. 3C, D).