Dioscorea namorokensis Wilkin, 2002

Wilkin, Paul, Hladik, Annette, Jeannoda, Vololoniaina & Weber, Odile, 2009, The threatened edible yams of the Dioscorea sambiranensis R. Knuth species complex (Dioscoreaceae): a new species and subspecies, Adansonia (3) 31 (2), pp. 249-266 : 258-260

publication ID

https://doi.org/ 10.5252/a2009n2a2

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scientific name

Dioscorea namorokensis Wilkin


2. Dioscorea namorokensis Wilkin  

Kew Bulletin 57: 902 (2002). — Type. Madagascar. Mahajunga , Soalala Subprefecture , Commune d’Andranomavo , Réserve naturelle intégrale Tsingy de Namoroka, NE side, 16°27’27”S, 45°23’26”E, 4.II.2000, ♂ fl., Wilkin   , Rakotonasolo & Davis 1126 (holo-, TAN!; iso-, K! [K000098740-3]) GoogleMaps   .


For description, illustration, specimen citations and supporting information see Wilkin et al. (2002). We have not seen any specimens collected since that paper was published.


Dioscorea namorokensis   appears to be endemic to the Réserve naturelle intégrale Tsingy de Namoroka.The EOO and AOO of D. namorokensis   are unknown because there are insufficent collections to calculate them (four specimens from two localities in the NE part of Namoroka). Thus its provisional IUCN red list assessment ( IUCN 2001) must be DD. However, even if it was found over the whole of Namoroka (c. 95 km 2) its EOO and AOO would be small enough to place it in a threatened category, probably EN or CR. Based on the specimens available, its AOO would be c. 2 km 2, with a cell width of 2 km and one locality. It is unlikely to occur outside Namoroka given the different soils and lack of dense woody vegetation in the surrounding area.

3. Dioscorea pteropoda Boivin ex H.Perrier Mémoires de la Société   linnéene de Normandie, Nouvelle Série, Section Botanique 1 (2): 17 (1928); Burkill & Perrier de la Bâthie in Humbert , Flore de Madagascar et des Comores, 44e famille: 51 (1950). — Type : Madagascar. Antsiranana Province, Antsiranana II District, Lanivato ( Liny Vatou ), 1835, ♂ fl. & ♀ immat. fr., Bernier 265 (2e envoi), (lecto-, P! [P00442458], selected here; isolecto-, P! [P00442459 & P00442460]). Remaining former syntypes: Madagascar. Antsiranana Province, Antsiranana II District, Lanivato ( Liny Vatou ), Boivin 2343, 1846, ♂ fl. & ♀ immat. fr. (P! [P00442461-3]). — Lanivato ( Liny Vatou ), 1840, ♂ fl., Bernier s.n. (K! [K000099031]) OTHER MATERIAL EXAMINED. — Madagascar. Antsiranana Province, Antsiranana II District, 5 km from Andranomena , on the road towards Sahafary forest , 12°35’10.6”S, 49°27’38.1”E, 26.IV.2008, ♀ fr., Andriamahay & Rakotoarisoa 2000 (K!, SNGF). — Collines et plateaux calcaires de l’Analamera, I.1938, ♂ fl., ♀ fl. & immat. fr., Humbert 19163 (K!, P!). — Analamera, along Ambatabe River , 12°40’25”S, 49°32’40”E, 7.I.2002, ♂ fl., De Block, Rakotonasolo & Randriamboavonjy 1104 (BR, K!, MO, TAN). — Ambilobe District , collines et plateaux calcaires de l’Ankarana du Nord, 29.II.1960, ♂ fl., ♀ fl. & immat. fr., Humbert & Cours 32769 (P!). — Collines et plateaux calcaires de l’Ankarana du Nord, 29.II.1960, ♀ immat. fr. Humbert & Cours 32780 (BR, P!). — Mont Ambohipiraka au nord-est d’Ambilobe (Vallée du Mananjeba), 3.II.1960, ♀ immat. fr. Humbert & Cours 32877 (P!). — Mont Ambohipiraka au nord-est d’Ambilobe (Vallée du Mananjeba), 3.II.1960, ♂ fl., Humbert & Cours 32878 (K!, P!). — Ankatoto, Mont Ambohipiraka, 5.II.1960, ♂ fl., Cours & Humbert 5658 (P!). — Ambilomagodro, km 114, Montagne Ambohibe, 8.II.1960, ♂ fl. & ♀ fl. & immat. fr., Cours & Humbert 5699 (P!). — Collines et plateaux calcaires de l’Ankarana, forêt près d’Ambodimagodro, XII.1937 - I.1938, ♀ fl. & immat. fr., Humbert 19038 (K!, P!). — Massif de l’Ankarana , Ambilamagodro, partie ouest, 13°00’46”S, 49°07’51”E, 31.I.2003, ♀ fl., Bardot-Vaucoulon, Andriananantoanina & Manesy 1384 (MO, P!, TAN). — Massif de l’Ankarana , Ambilamagodro, partie ouest, 13°00’46”S, 49°07’51”E, 31.I.2003, ♂ fl., Bardot-Vaucoulon, Andriananantoanina & Manesy 1384bis (MO, P!, TAN). — Vohemar District , commune rurale de Daraina, Daraina, forêt de Solaniampilana-Maroadabo à 580 m du point cote 214, au 90°, 10.III.2004, ♀ fr., Gautier, Wohlhauser, Nusbaumer & Ranirison LG 4539 (G, K!) GoogleMaps   .


A twining vine to about 2 m in height, stems annual from a fleshy tuber.Tuber 1.2-1.5 m long and 5-7.5 cm in diameter according to label of Bernier 265 (2e envoi) collected in 1835, apparently not investigated since. Indumentum wholly absent. Stems left-twining, to c. 2 mm in diameter, terete, unarmed, drying smooth and dull brown to redbrown, lower stem and cataphylls not seen. Bulbils not present. Leaves alternate, blade 2.2-6.7 × 1.5-5.2 cm, ovate to broadly so to ovate-deltoid, broadly so or orbicular-deltoid, coriaceous, dark green and sometimes glossy above, paler green to glaucous-green or grey-green below, drying olivegreen to brown above, grey-green below, sometimes with a reddish hue, margins entire, base cordate to shallowly so or rarely truncate, sinus 2-12 mm deep, smaller in leaves towards vegetative shoot tips and in fertile shoots, apex 4-13 mm long, acute to acuminate with a 0.8-3.6 mm long, deltoid to narrowly deltoid, thickened, concolorous to dark brown forerunner tip, veins (3 or) 5 to the apex, with a bifid vein or pair of veins to both sides of the base, both primary and secondary veins prominent on both leaf blade surfaces; petiole 9-26 mm long, to 2.5 mm in width (including wings), flattened, channeled above and strongly winged on both sides, usually reddish-brown, blotched on wings, darker at base and apex, wings sometimes excurrent at apex onto basal vein for a few mm; lateral nodal spines (“stipules” of Burkill 1960) not present but petiole base also winged and partially to wholly amplexicaul, resulting on an ovate or elliptic winged petiole base, and sometimes the whole node, to 6 mm in diameter. Inflorescences one per axil, simple, pendent. Male inflorescences racemose, primary axis 1.5-11.8 cm long (including 4-16 mm long sterile basal region), flattened and possessing narrow wings, with up to 25 nodes c. 2-6 mm apart, each with a lax cymule of 3-5(-8) flowers, reduced to 2 flowers per cymule or rarely solitary flowers towards the apex, cymule bract 0.8-2.0 mm long, narrowly elliptic to very narrowly ovate, thickly membranous with a thicker midrib, apex long-acuminate, bracteoles not present, cymule primary branch 0.4-2.3 mm long. Female inflorescences to 4 cm long, racemose, axes flattened and angled to more or less terete, sometimes winged, bearing 1 to 5 solitary flowers on the apical part, 5-7 mm apart on the axis. Male flowers scent not recorded, pedicels 0.5-2.9 mm long, weakly clavate, 0.2-0.55 mm in diameter at apex, ridged, one floral bract at each pedicel base, 0.35-1.5 × 0.15-0.6 mm, size diminishing towards cymule apex, narrowly elliptic to narrowly lanceolate, basal bracts of cymule sometimes narrowly ovate or lanceolate, apical bracts sometimes sublinear, apex always long-acuminate; tepal whorls not differentiated, free or slightly fused at base, erect in most flowers (presumably post/pre anthesis) but fully open and rotate in one or two flowers per inflorescence, inserted on a discoid torus 0.6-1.2 mm in diameter, only thickened around the pistillode and area of filament insertion, marginal texture as tepals, tepals 6, 0.7-1.6 × 0.4-1.1 mm, ovate to broadly so, elliptic or elliptic-oblong, thickly membranous, apex acute to obtuse; stamens erect, filaments 0.1-0.3 mm long, filiform, inserted in two triangular whorls around pistillode towards torus centre, anthers 0.15-0.3 × 0.15-0.3 mm, ovoid-oblongoid, dorsifixed and therefore making a T-shape with filament, pale yellow; pistillode a 3-lobed, subconical central projection to c. 0.3 mm long, drying dark brown. Female flowers scent not recorded, each on a long stalk comprising a (0.6-) 1.3-2.6 mm long primary branch (from basal bract to floral bracteole) and a 1.1-1.9 mm long pedicel (from floral bract to ovary base), both flattened and ridged, basal bract (equivalent to cymule bract in male inflorescence) 1.1-1.6 × 0.3-0.4 mm, lanceolate to narrowly so, apex acuminate, thickly membranous, midrib thicker, floral bract like basal bract but smaller; ovary c. 5.3-7.5 mm long, 3-angled, narrowly elliptic to narrowly lanceolate in outline; tepals not differentiated into 2 whorls, 6, 1.3-1.9 × 0.9-1.3 mm, ovate to oblong ovate, acute to obtuse, inserted on a flat, discoid torus 1.3- 1.6 mm in diameter; staminodia 6, 0.2-0.4 mm long, erect to ascending, clearly staminiform to scarcely differentiated, filamentodes inserted around style bases; styles/stigmas 3, 0.4-0.5 mm long, fused at base to form a broad column, free and reflexed above with the bifid stigmas at the tips of its horizontal branches, diameter c. 1.2 mm. Capsule 2.7-4.6 × 1.7-2.7 cm, on a 5-10 mm long stipe, ascending at c. 70-45° to axis at dehiscence, elliptic to obovate or broadly so in outline, rounded at base and apex, capsules collected before dehiscence drying pale tan and “double wing” (where thin exocarp develops beyond endocarp giving an appearance like a submarginal vein; Fig. 1H View FIG ) often only weakly developed; mesocarp absent even at maturity. Seeds (immature only) c. 6.2 × 4.2 mm, chestnut-brown, flattenedovoid, winged at base only, wing c. 10 × 5.5 mm, membranous, translucent golden-brown.


The lectotype above was selected because it is the most representative specimen of those sheets and did not comprise mixed male and female material. One specimen of D. pteropoda, d’Alleizette 1407   was collected near Toamasina in eastern Madagascar according to the label. Th is locality is undoubtedly erroneous   .


Dioscorea pteropoda   has been collected near Daraina and Ambilobe, in the Réserve spéciale d’Ankarana and at Lanivato and Analamera in Northern Madagascar (see Fig. 3). It is found in dry, semideciduous to deciduous forest with a low canopy, occurring in dense forest but sometimes persisting in regularly burnt or degraded areas with mixed grassland and shrubs, at altitudes from 40 to 400 m. Dioscorea pteropoda   is often associated with limestone, or more rarely with sandstone, and has been found on red sand and sandy clay soils. It can be associated with, for example baobabs, Pachypodium Lindl.   and Adenia Forssk.   as at Analamera.


Totongana (Analamera), Ovifotsy (Lanivato). The name Totongana is applied to an Aristolochia   species at Antrema near Mahajanga.


Tuber edible cooked.


The EOO of D. pteropoda   is 2335 km 2, and its AOO is 789 km 2 using a cell width of 9.36 km; it occupies nine cells. The former suggests that the appropriate IUCN red list assessment is EN, and the latter VU ( IUCN 2001). Rapoport Analysis ( Rapoport 1982) gives an area of 1657 km 2 and four subpopulations. AOO also indicates that there are four subpopulations. Unfortunately many of the known localities are outside the protected area of the Réserve spéciale d’Ankarana ( Fig. 3) and thus under greater theat of habitat loss. Levels of exploitation of wild yams in Northern Madagascar are high as stated above. Thus we suggest a provisional IUCN red list assessment of VU B1ab(iii,v); B2ab(iii,v).