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One of Kew's most striking recent discoveries is Dioscorea strydomiana - a critically endangered yam from South Africa. Only two populations totaling about 200 plants are known in the wild. This species is believed to provide a cure for cancer in the region where it grows, and is consequently under threat from over-exploitation by medicinal plant collectors, who remove parts of the tubers. D. strydomiana was named by Kew botanist Paul Wilkin in honour of the late Gerhard Strydom, who, with Johan Hurter, played a significant role in the discovery of this species when he worked for the Mpumalanga Parks Board.

Dioscorea strydomiana (Strydom's yam)

[KSP]

Kew Species Profiles

General Description

Dioscorea strydomiana is a recently discovered yam from South Africa. It is critically endangered and one of the most unusual yam species anywhere in the world.

Only two populations totaling about 200 plants are known in the wild. This species is believed to provide a cure for cancer in the region where it grows, and is consequently under threat from over-exploitation by medicinal plant collectors, who remove parts of the tubers. D. strydomiana was named by Kew botanist Paul Wilkin in honour of the late Gerhard Strydom, who, with Johan Hurter, played a significant role in the discovery of this species when he worked for the Mpumalanga Parks Board.

Species Profile
Geography and distribution

Dioscorea strydomiana is restricted to Mpumalanga in South Africa, where it has been recorded at 1,100 - 1,150 m above sea level. It has been found growing in open acacia woodland with aloes and a grass-rich understory on steep, rocky slopes.

Description

Dioscorea strydomiana does not look like a typical yam (member of the genus Dioscorea ) because it is shrub-like with a huge, slow-growing,'lumpy' wooden tuber which is mostly above ground. The tuber can reach 1 m in height and diameter; multiple shoots sprout from one or more shoot-bearing branches on it each spring, although young tubers have a single shoot-bearing tip. The outer layer of the tuber is 'corky' and grooved with numerous vertical furrows. The plant as a whole grows to about 1.5 m tall.

One to several non-twining stems to about 10 mm in diameter grow from each shoot-bearing tip each growing season. The branches spread more or less horizontally, at least at the bases, to give a dense shrub-like habit. The leaves are borne alternately on the stem. The leaf blade is 15-41 × 6-20 mm, thickly papery and stiff at maturity, with 3 or 5 veins running to the tip. The leaves are dull pale green on both surfaces and the petiole (leaf stalk) and main veins are pale whitish-green and often translucent.

There is one simple, racemose inflorescence per axil (the angle between a stem and a leaf) with only a few flowers per inflorescence. The male inflorescences are 16-53 mm long, with a peduncle (flower stalk) 9-14 mm long. The flowers are solitary or in pairs, with bracts present. The female inflorescences are 14-51 mm long, with a peduncle 11-28 mm long and with bracts on the pedicel. The flowers have 6 papery tepals, which are pale cream-yellow with a dark green longitudinal central stripe.

The capsule is 18-20 × 17-20 mm. The seeds are 4-7 × 3.5-6 mm (excluding the wing), dull, matt, mid to dark brown, and smooth to the naked eye but rough when viewed through a microscope. The seeds are winged at the tip or with a narrow wing on the side, and sometimes the base, of the seed. The wing is 6-12 × 6-9.5 mm, membranous and pale to chestnut brown, darker towards the seed.

Threats and conservation

So far, only two populations of Dioscorea strydomiana have been found. A team visits those populations on a regular basis to assess their status. It is estimated that each population comprises about 100 plants. On the last visit, the team noted that one population had suffered significant damage from medicinal plant collectors, who remove parts of the tuber. Dioscorea strydomiana is thought to be slow-growing and therefore slow to recover from such damage. Burning, mining, cattle farming, firewood collection, porcupine activity and removal of plants for the horticultural trade are thought to be further threats to the species. Like almost all Dioscorea species it is dioecious (separate male and female plants) so only the female element of the populations produce seed. It has been rated as Critically Endangered (CR) according to IUCN Red List criteria.

A number of measures have already been taken to protect this species. Careful monitoring by members of the Mpumalanga Tourism and Parks Authority (MTPA), the South African National Biodiversity Institute (SANBI) and the Mpumalanga Plant Specialist Group, has found that its numbers are declining at an alarming rate, so that urgent measures to promote its sustainable use and conservation have been called for. The area in which the species grows is not yet protected, but is monitored by the local tribal authority in collaboration with the MTPA in an attempt to prevent unscrupulous and illegal collection of plant material. An attempt to set up a community-run nursery in the area to provide cultivated plants for the medicinal and horticultural trade has so far not proved successful, but collections of seed-grown individuals have been successfully established in two of SANBI's National Botanical Gardens (NBGs). Two seed collections have been banked at Kew's Millennium Seed Bank.

Uses

Dioscorea strydomiana is used locally with another species of Dioscorea to treat cancer. Its efficacy is unknown. The related species D. elephantipes and D. sylvatica are known to contain high levels of steroidal compounds which can be used to reduce inflammation, for example in the treatment of arthritis or for the promotion of healing.

Millennium Seed Bank: Seed storage

Kew's Millennium Seed Bank Partnership aims to save plant life world wide, focusing on plants under threat and those of most use in the future. Seeds are dried, packaged and stored at a sub-zero temperature in our seed bank vault.

Number of seed collections stored in the Millennium Seed Bank: Two

Germination testing: About 55%

Where to see this at Kew

Pressed and dried specimens of Dioscorea strydomiana are held in the Herbarium, one of the behind-the-scenes areas of Kew. The details of some of these specimens can be seen online in the Herbarium Catalogue.

Distribution
South Africa
Ecology
Open woodland with a grass-rich understorey on steep, rocky, south-east to south-south-east facing slopes on soils over dolerite (sub-volcanic rock) with quartzite intrusions.
Conservation
Rated as Critically Endangered (CR) according to IUCN Red List criteria.
Hazards

None known.

[KBu]

Wilkin, P., Burrows, J., Burrows, S. et al. 2010. A critically endangered new species of yam (Dioscorea strydomiana Wilkin, Dioscoreaceae) from Mpumalanga, South Africa. Kew Bulletin 65: 421. DOI: https://doi.org/10.1007/s12225-010-9227-y

Conservation
In October 2008 the area where this species occurs was surveyed by a team of researchers and it was found to have two populations each of c. 100 plants. One population had been severely damaged by medicinal plant collectors (see below) who remove parts of the tuber, while the other was unaffected. This is a significant problem in what is probably a slow-growing species. The team estimated a 60:40 male:female ratio with 8% being juvenile plants. More recently, porcupine damage to tubers has been observed. Hurter (2003) stated that he had found less than 100 individuals in one population, and highlighted the threats of burning, mining, cattle farming and firewood collection to this species in addition to collection for medicinal use. He also believed it to be potentially threatened by collection for the horticultural trade. A preliminary study made by Strydom and Hurter in June 2000 (van Wyk & Hurter 2003) suggested that a survey of the single known population revealed that there were 107 plants, of which just c. 40 were mature and just 9 female. Thus a conservation status of Critically Endangered (CR B1ab(v) + 2ab(v); C1) (IUCN 2001) is indicated given that it is likely that there are less than 250 living individuals of this species, that it is threatened as detailed above and that it is a slow-growing and dioecious species.
Distribution
Endemic to Mpumalanga in South Africa.
Ecology
Open woodland with a grass-rich understory on steep, rocky, SE to SSE facing slopes on dolerite with quartzite intrusions; 1100 − 1150 m. The dominant species of the vegetation are Acacia caffraWilld., Acacia ebutsiniorum P. J. H. Hurter, Aloe pretoriensis Pole-Evans, Aloe marlothii A. Berger, FaurearochetianaChiov. ex Pic. Serm. subsp. speciosa (Welw.) Troupin, Calpurnia glabrataBrummitt, Vitex obovata E. Mey, Protea caffraMeisn. subsp. falcata (Beard) Lötter, ThemedatriandraForssk. and a Pelargonium species. Research into the ecology of Dioscoreastrydomiana, for example into its reproduction and recruitment, is highly desirable to inform its conservation.
Morphology General Habit
An erect shrub to c- 1.5 m, stems annual from a caduciform woody tuber
Morphology General Indumentum
Indumentum wholly absent
Morphology Leaves
Leaves alternate, held erect to ascending at c- 45° on more or less horizontal to ascending shoots, blade 15 – 41 × 6 – 20 mm, thickly chartaceous and stiff at maturity, with 3 or 5 veins to the apex, margins entire but appearing to have tiny auricles where channelled petiole is inserted onto leaf base; most leaves narrowly ovate to elliptic, elliptic-oblong, ovate or (narrowly) ovate-trapeziform, base obtuse to cuneate, apex weakly and shallowly retuse to acute with an acute to short-acuminate 0.8 – 2 mm long forerunner tip; a few 5-veined leaves ovate, broadly elliptic or obovate to rotund or obovate, rarely orbicular or transversely elliptic, base obtuse to broadly cuneate, apex retuse, bearing a 1.5 – 4.3 mm long forerunner tip; all leaves dull pale green on both surfaces, petiole and main venation pale whitish-green and often translucent, lower epidermis (at × 40 or × 60) reticulate, translucent; forerunner tip thickened, concolorous to brown or grey in 3-veined leaves, brown to very dark brown or dark grey in 5-veined leaves, undulately ridged, sometimes (more frequently in larger forerunner tips of 5-veined leaves) with pits surrounded by necrotic tissue on tip or adjacent parts of blade; primary and secondary veins shallowly impressed on upper surface, prominent below; petiole 2 – 6 × 0.4 – 1.5 mm (broader element of range in 5-veined leaves), with short basal and apical pulvinii, channelled above, cream-green, concolorous with and translucent like main veins in both fresh and dried material, base expanded and deltoid; cataphylls present at lower branch bases as stout, rather brittle, broadly deltoid, rigid projections (petiole base remains) often with apices broken off and with age reduced to ridges below the lower stem branches; lateral nodal flanges (“stipules” of Burkill1960) and bulbils not present
Morphology Reproductive morphology Flowers
Flowers with a shallowly saucer-shaped torus which is concolorous with pedicel to purplish-brown, when dry green to brown; tepals 6, narrowly oblong to narrowly oblong-elliptic or oblanceolate, inserted at torus apex in 2 un- or scarcely differentiated whorls (inner slightly broader), chartaceous, pale cream yellow with a dark green longitudinal central stripe, when dry pale tan-yellow to brown-yellow with an apparently broader stripe; bases ascending at c- 45°, apices obtuse to acute and reflexed to recurved at anthesis, floral scent unknown; male flowers on 2 – 6 mm long pedicels (including parts above and below floral (upper) bract) which are weakly clavate and terete in cross-section but longitudinally ridged; cymule primary branch (where present) 1.1 – 2.3 mm long, branch and pedicel concolorous with axis; floral bracts 1.1 – 2 × 0.4 – 0.9 mm long, ovate to narrowly so, membranous, pale tan to red-brown, apex acuminate; torus 0.8 – 1.4 × (1.3 –) 1.7 – 1.9 mm; tepals 3.8 – 4.9 × 1.1 – 1.7 mm (length including torus from which they are not clearly differentiated); filaments 6, (0.8 –) 1.1 – 1.6 mm long, inserted on longitudinal stripe towards tepal bases, incurved towards its apex so that the basifixed anthers are held ±horizontally in a loose cluster above the pistillode, anthers 0.6 – 1.2 × 0.35 – 0.8 mm long, narrowly oblongoid to ellipsoid; pistillode 1.3 – 1.7 mm long, narrowly ovoid, longitudinally 3-ridged, erect, apex acuminate, entire; female flowers on 3.2 – 8.4 mm long (longer element of range in immature capsules) angled and ridged pedicels which are concolorous with ovary/developing capsule, especially towards apex; floral bracts as in male flowers; ovary c- 4 – 5 × 1.5 – 2.5 mm, narrowly oblongoid with three blunt longitudinal ridges, rapidly developing into an immature capsule, mid-green, paler on the ridges and the latter with purple margins, when dry light to mid brown, often with patches of white or cream speckling (seen at × 40 or × 60 to be thickened parts of the epidermis of variable thickness, distribution and texture); torus subtended by a 0.1 – 1.1 mm long, broad stipe, 0.2 – 0.6 × 1.9 – 2.3 mm; tepals 2.8 – 4.1 × 1.0 – 1.4 mm; staminodia 6, 0.6 – 0.8 mm, inserted near tepal bases, erect, filiform to staminiform; styles 3, fused to form a 1.7 – 2.5 mm long, stout, erect, cylindric to 3-ridged column, 3-lobed and 1 – 1.2 mm in diam- at its apex, each lobe recurved and bifidly split into 2 flat, ovate stigmatic lobes with acute apices, patent to stylar column
Morphology Reproductive morphology Fruits
Capsule (15 –) 18 – 20 × (16 –) 17 – 20 mm, broadly obovate to broadly obovate-elliptic, borne erect (i.e. not reflexing as in pendent inflorescences) at c- 15 – 45° to axis at dehiscence, base cuneate, apex shallowly retuse, floral stipe, torus and sometimes tepals (in part) persistent at capsule apex to dehiscence, opening to c- ¼ to ⅓ of its depth; capsule lobe apices weakly recurved to expose wing apex and smooth, glossy, straw-coloured inner surface of endocarp, outer pericarp pale straw-brown with dense red-brown to dark red-brown flecking, sometimes with a greyish hue or fragmenting, especially near axis at dehiscence, to reveal outer surface of endocarp
Morphology Reproductive morphology Inflorescences
Inflorescences 1 per axil, simple, racemose, erect to ascending, axes stout, terete to ridged, concolorous with distal stems, flowers held erect to ascending at anthesis, few per inflorescence towards shoot apices, especially in female plants; male inflorescences 16 – 53 mm long, peduncle 9 – 14 mm long, flowers solitary or in cymular pairs, bracts present at pedicel base and at from c- ¼ to ¾ of its length (solitary flowers) or at cymule base and branching point (paired flowers); female inflorescences 14 – 51 mm long, peduncle 11 – 28 mm long, bracts 1 or 2 at pedicel base or 1 at base and 1 higher on pedicel
Morphology Reproductive morphology Seeds
Seeds variable, 4 – 7 × 3.5 – 6 mm (excluding wing) thinly lenticular to ovoid-lenticular, in the latter the longer axis horizontal to vertical, dull, matt, mid to dark brown, smooth to the naked eye but roughened to weakly striate under the dissecting microscope; winged at apex only or with a narrow (to c- 1.5 mm wide) wing on the side and sometimes base of the seed, continuous with the main wing, never winged in area where the seed is inserted on the placenta, sometimes with an acute projection of the testa at the base to c- 1 mm long; wing 6 – 12 × 6 – 9.5 mm, oblong-elliptic to oblong-ovate, obovate or obovate-obtrapezoidal to broadly so, sometimes longitudinally asymmetric, apex acute to truncate, rarely weakly retuse, membranous and translucent to thinly chartaceous and opaque, sometimes appearing longitudinally rugose or bullate especially where thicker, pale to chestnut brown, darker towards seed, under the dissecting microscope appearing to be clear and translucent with a network of branching and anastomosing darker opaque fibres, the density of the fibres determining the colour and level of translucence of any part of the wing, margin entire to weakly, shallowly and irregularly lobed
Morphology Stem
Stems 1 to several per shoot-bearing apex per growing season, to 10 mm in diameter, subterete, unarmed, fistulose, erect to ascending, smooth to weakly longitudinally ridged, grey-green with a purple hue to dull red-brown, drying pale to red-brown or olive green, much branched, internodes a few cm apart and branches spreading ±horizontally at least at bases to give a dense, shrub-like habit, not twining even at the apices but retaining a residual left twist, dead stems of previous seasons often persisting
Note
The only non-climbing Dioscorea species in South Africa in addition to those of the Testudinaria group is D. brownii, a rare endemic of KwaZulu Natal (Scott-Shaw 1999). It has a subterranean, elongate, probably horizontal, woody tuber a few cm in diam., with a flaky, bark-like outer layer. Its stems when dry have strong longitudinal ridges and grooves, and are wholly unbranched, and its leaves are narrowly lanceolate to oblong-lanceolate, with 5 – 7 closely spaced parallel veins and a long-acuminate apex (at least in flowering shoots). The tepals of D. brownii are held erect, and are sometimes weakly recurved at the apices, giving the flower a campanulate appearance. They are not more than 3.2 (male) or 2.5 (female) mm long. The maximum capsule dimensions are 22 × 15 mm; thus the shape differs from D. strydomiana. It is unlikely that they could be confused. The leaves of juvenile plants (up to five years old) cultivated from seed at the Lowveld Botanical Gardens in Mpumalanga are narrowly triangular- or oblong-ovate to broadly ovate in shape and have cordate bases. More research is needed on leaf development and morphology in this species. Dioscoreastrydomiana was named for the late Gerhard Strydom, who, with Johan Hurter, played a significant role in the discovery of this species when he worked for the Mpumalanga Parks Board. The seeds have been banked at the RBG, Kew Millennium Seed Bank (accession no: 0247928, 3121 seeds, 600-08A) as indicated by Hurter (2003) and van Wyk & Hurter (2003).
Vegetative Multiplication Tubers
Tuber below substrate unknown, above soil to c- 1 × 1 m, subglobose with a single shoot-bearing apex when young to irregularly cylindric-ovoid with age and branching into several apices from which shoots are initiated; outer “corky” layer divided by furrows into projections, in young plants projections with oblong to irregular polygonal bases a few cm across, to c- 8 cm long, narrowing towards apex and pyramidal to irregularly polyhedral but always pointed, horizontally marked with brown to pale grey (annual?) striations, with age corky layer charred black, with low dome-shaped elements to c- 3 cm thick and 10 cm wide/long, tuber internal tissue woody, white

[KSP]
Use
Medicinal.

[KBu]
Use
A medicinal plant in the local pharmacopeia. It is said to be used with another species of Dioscorea to treat cancer. Steroidal compound levels are known in to be very high in the related species D. elephantipes and D. sylvatica (Coursey1967; Martin 1969). Thus it is likely that extracts of D. strydomiana may also be used to treat conditions of inflammatory origin such as arthritis or to promote healing. Both D. elephantipes and D. sylvatica were widely exploited as a source of diosgenin in South Africa in the 1950s, with the scale of use necessitating a government licensing scheme (Coursey1967).

Native to:

Northern Provinces

English
Strydom's yam

Dioscorea strydomiana Wilkin appears in other Kew resources:

Date Reference Identified As Barcode Type Status
Jan 1, 2010 Hurter, P.J.H. [106], South Africa K000524243
Jan 1, 2010 Burrows, J.E. [10627A] 65346.000
Jan 1, 2010 Hurter, P.J.H. [106], South Africa K000524244
Burrows, J.E. [10627A], South Africa K001148769
Lukhele, V. [UPP 33], South Africa K001148768

First published in Kew Bull. 65: 425 (2010 publ. 2011)

Accepted by

  • Govaerts, R., Nic Lughadha, E., Black, N., Turner, R. & Paton, A. (2021). The World Checklist of Vascular Plants, a continuously updated resource for exploring global plant diversity. https://doi.org/10.1038/s41597-021-00997-6 Scientific Data 8: 215.

Literature

Kew Bulletin

  • Abbott, A. T. D. (1998). The rediscovery of Dioscoreabrownii. PlantLife 18: 29.
  • Archibald, E. E. A. (1967). The genus Dioscorea in the Cape Province West of East London. J. S. African Bot. 33: 1 – 46.
  • Baker, J. G. (1897). Dioscoreaceae. In: W. T. Thistleton-Dyer (ed.), Flora Capensis. Lovell Reeve & Co., London.
  • Born, J., Linder, H. P. & Desmet, P. (2007). The Greater Cape Floristic Region. J. Biogeogr. 34: 147 – 162.CrossRefGoogle Scholar
  • Burchell, W. J. (1824). Travels in the Interior of Southern Africa. Vol. 2. Longman, Hurst, Rees, Orme & Brown, London.
  • Burkill, I. H. (1939). Notes on the genus Dioscorea in the Belgian Congo. Bull. Jard. Bot. État. Bruxelles 15: 345 – 392.CrossRefGoogle Scholar
  • Coursey, D. G. (1967). Yams: An Account of the Nature, Origins, Cultivation and Utilisation of the Useful Members of the Dioscoreaceae. Longmans, London.
  • Govaerts, R. & Wilkin, P. (2009). World Checklist of Dioscoreaceae. The Board of Trustees of the Royal Botanic Gardens, Kew. Published on the Internet, http://www.kew.org/wcsp/monocots/. Accessed 16 May 2009.
  • Hammer, Ø. & Harper, D. A. T. (2006). Palaeontological Data Analysis. Blackwell, Oxford.
  • Hurter, P. J. H. (2003). A new pachycaulDioscorea species from Mpumalanga Province, South Africa and its conservation. Aloe 40: 73 – 75.
  • IUCN (2001). IUCN Red List Categories and Criteria. Version 3.1. Prepared by the IUCN Species Survivial Commission, Gland, Switzerland & Cambridge, UK.
  • Knuth, R. (1924). Dioscoreaceae. In: A. Engler (ed.), Das Pflanzenreich IV. 43. Reprinted 1957, H. R. Engelmann (J. Cramer), Weinheim/Bergstr., Germany.
  • Kulkarni, M. G., Street, R. A. & van Staden, J. (2007). Germination and seedling growth requirements for propagation of Dioscoreadregeana (Kunth) Dur. and Schinz — A tuberous medicinal plant. S. African J. Bot. 73: 131 – 137.CrossRefGoogle Scholar
  • Martin, F. W. (1969). The species of Dioscorea containing sapogenin. Econ. Bot. 23: 373 – 379.CrossRefGoogle Scholar
  • Miege, J. (1968). Dioscoreaceae. In: F. N. Hepper (ed.), Flora of West Tropical Africa, ed. 2, pp. 144 – 154. Crown Agents, London.
  • Milne-Redhead, E. (1975). Dioscoreaceae. In: R. M. Polhill (ed.), Flora of Tropical East Africa. Crown Agents, London.
  • N’Kounkou, J. S. (1993). Les Dioscoreaceae du Congo. Fragm. Florist. Geobot., Suppl. 2: 139 – 182.
  • Rowley, G. D. (2001). Dioscorea. In: U. Eggli (ed.), Illustrated Handbook of Succulent Plants: Monocotyledons, pp. 261 – 272. Springer Verlag, Berlin.
  • Scott-Shaw, R. (1999). Rare and Threatened Plants of KwaZulu-Natal and Neighbouring Regions. KwaZulu-Natal Conservation Service, Pietermaritzburg, South Africa.
  • Smith, P. P., Burgoyne, P. & van Wyk, E. (2001). Rare plants Rediscovered in the Northern Cape. (http://www.sabonet.org.za/collecting/collecting_southafrica_northerncape.htm).
  • Van Wyk, E. & Hurter, P. J. H. (2003). Royal Botanic Gardens, Kew Millennium Seed Bank Project Plant Story: Dioscorea sp. (http://www.kew.org/msbp/plantstories/Dioscorea.htm).
  • Von Teichman und Logischen, I., van der Schijff, H. P. & Robbertse, P. J. (1975). The genus Dioscorea L. in South Africa. Boissiera 24: 215 – 224.
  • Wilkin, P. (2001). Yams of South-Central Africa. Kew Bull. 56: 361 – 404.CrossRefGoogle Scholar
  • ____ & Sebsebe D. (1996). Dioscoreaceae. In: S. Edwards, Sebsebe D. & I. Hedberg (eds), Flora of Ethiopia and Eritrea, Vol. 6, Hydrocharitaceae to Araceae, pp. 55 – 62. The National Herbarium, Biology Department, Science Faculty, Addis Ababa University, Addis Ababa and Department of Systematic Botany, Uppsala University, Uppsala.
  • ____ (1952). Testudinaria as a section of the genus Dioscorea. J. S. African Bot. 18: 177 – 191.
  • ____ (1960). The organography and the evolution of the Dioscoreaceae, the family of the yams. Bot. J. Linn. Soc. 56: 319 – 412.CrossRefGoogle Scholar
  • ____ (2009). Dioscoreaceae. In: J. Timberlake (ed.), Flora Zambesiaca 12(2): 109 – 140. Royal Botanic Gardens, Kew.
  • ____, Schols, P., Chase, M. W., Chayamarit, K., Furness, C. A., Huysmans, S., Rakotonasolo, F., Smets, E. & Thapyai, C. (2005). A Plastid Gene Phylogeny Of The Yam Genus, Dioscorea: Roots, Fruits And Madagascar. Syst. Bot. 30: 736 – 749.CrossRefGoogle Scholar
  • ____, ____ & Ryan, P. D. (2001). PAST: Palaeontological Statistics Software Package for Education and Data Analysis. Palaeontologia Electronica 4. Available at http://palaeo-electronica.org/2001_1/past/issue1_01.htm.

Kew Species Profiles

  • IUCN (2001). IUCN Red List Categories and Criteria. Version 3.1. Prepared by the IUCN Species Survival Commission, Gland, Switzerland & Cambridge, UK.
  • Wilkin, P., Burrows, J., Burrows, S., Muasya, A.M., van Wyk, E. (2010). A critically endangered new species of yam ( Dioscorea strydomiana Wilkin, Dioscoreaceae) from Mpumalanga, South Africa. Kew Bull.

Herbarium Catalogue Specimens
Digital Image © Board of Trustees, RBG Kew http://creativecommons.org/licenses/by/3.0/

Kew Backbone Distributions
The International Plant Names Index and World Checklist of Selected Plant Families 2021. Published on the Internet at http://www.ipni.org and http://apps.kew.org/wcsp/
© Copyright 2017 World Checklist of Selected Plant Families. http://creativecommons.org/licenses/by/3.0

Kew Bulletin
Kew Bulletin
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Kew Names and Taxonomic Backbone
The International Plant Names Index and World Checklist of Selected Plant Families 2021. Published on the Internet at http://www.ipni.org and http://apps.kew.org/wcsp/
© Copyright 2017 International Plant Names Index and World Checklist of Selected Plant Families. http://creativecommons.org/licenses/by/3.0

Kew Species Profiles
Kew Species Profiles
http://creativecommons.org/licenses/by-nc-sa/3.0