Clarifying the Dioscorea buchananii Benth. species complex: a new potentially extinct subspecies for South Africa
Author
Wilkin, Paul
Royal Botanic Gardens, Kew, Richmond, Surrey, TW 9 3 AB, UK
p.wilkin@kew.org
Author
Muasya, A. Muthama
Department of Botany, University of Cape Town, Private Bag X 3, Rondebosch 7701, SOUTH AFRICA
text
PhytoKeys
2015
2015-04-15
48
51
72
http://dx.doi.org/10.3897/phytokeys.48.6806
journal article
http://dx.doi.org/10.3897/phytokeys.48.6806
1314-2003-48-51
FFF19E64FFB4FFDEFFBE0F54FFC2FFF5
576291
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
x
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
x
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
x
3 mm, deltoid, apex caudate, recurved (
fide
Archibald 1968). Leaves alternate, blade 20-104
x
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
x
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
x
0.6-1.3 mm, inner whorl 2.0-3.7
x
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
x
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
x
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
x
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
x
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
x
5.0-6.5 mm excluding wing, irregularly lenticular, dark brown, wing 10.5-18.8
x
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
1/4
way up pass, sterile 15 Nov 1961,
Archibald
7552 (K!); Victoria East, about
1/4
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!]).