How many species are there in the holomycotrophic genus Didymoplexis Griff. (Orchidaceae) in Madagascar? Author Cribb, Phillip The Herbarium, Royal Botanic Gardens, Kew, Richmond, Surrey TW 9 3 AB, United Kingdom. p.cribb@kew.org.uk Author Gautier, Laurent Conservatoire et Jardin botaniques de la Ville de Genève and Université de Genève, Laboratoire universitaire de Systématique végétale et Biodiversité, CP 60, 1292 Chambésy, Switzerland. Author Nusbaumer, Louis Conservatoire et Jardin botaniques de la Ville de Genève and Université de Genève, Laboratoire universitaire de Systématique végétale et Biodiversité, CP 60, 1292 Chambésy, Switzerland. text Candollea 2013 2013-07-01 68 1 41 49 journal article 20827 10.15553/c2013v681a3 6325a650-a553-43f1-a504-02d37424a5a8 2235-3658 6033898 Didymoplexis recurvata P. J. Cribb, Nusb. & L. Gaut., spec. nova ( Fig. 1 , 4 ). Typus: MADAGASCAR . Prov. Diego-Suarez/ Antsiranana : sous-préfecture de Vohemar, commune rurale de Daraina, forêt de Binara , 13°15’S 49°37’E , fl., 985 m , 12.XII.2005 , Nusbaumer & Ranirison 1763 bis ( holo- : G [ G00181978 ]! ; iso- : TAN !, research herbarium of Daraina). AffinisDidymoplexisavaratraensissed floribius albisvel roseis, sepalis petalisque latioribus, sepalis lateralibus tertiobasali adnatis, labello late obovato emarginato, callo elongato ad apicem trilobato et brachiisdolabriformibus pendentibus ad apicem columnae satis distinguenda. Holomycotrophic herb up to 10 cm tall, growing from a subterranean elongated blackish tuberous rhizome. Leaves scale like, very small. Inflorescence erect, racemose, laxly up to 6- flowered, the flowers opening one at a time and successively; peduncle slender, erect, bearing a small ovate bract below inflorescence, white; rachis terete, slender; pedicel with longitudinal ridges; bracts ovate, acute, 1.5-2 mm long. Flowers with white sepals and petals and a white to rose-pink lip with a yellow callus, the column buff flushed. Dorsal sepal erect, lanceolate, subacute, 7-8 × 4-5 mm ; lateral sepals adnate in basal third, ovate, rounded to subacute, 7-8 × 4-5 mm . Petals oblanceolate, acute, 7-8 × 5-7.5 mm , adnate in basal third to the sepals. Lip shortly narrowly clawed at base, very broadly obovate-spatulate, emarginate, 3.5-4 × 5-6 mm , slightly decurved at apex; callus on claw erect, dilated and 3-lobed at tip. Column 3.5-5 mm long, slender at base, strongly winged at apex, the wings dependent, recurved, rounded at tip, 1 mm long. Fruit unknown. Etymology. – The specific epithet refers to the column with recurved apical arms bilobed at the tips. Distribution. – The species is only known from the Binara forests in the Loky-Manambato (Daraina) region, in Antsiranana Province in North-East Madagascar. Only 15- 20 individuals were observed in one population in the Loky-Manambato region among the 54,000 plant occurrences recorded during the Loky-Manambato vegetation study ( NUSBAUMER, 2011 ). Habitat and ecology. – Didymoplexis recurvata was recorded in evergreen montane forest on metamorphic rock; at 985 m . This terrestrial herb occurs in forests with canopies reaching 11 to 15 m , emergent trees reaching 21 to 24 m and with a second aborescent stratum at 8 to 10 m , with two woody strata at 5 to 7 m and at 1 to 2 m high, and with a no herbaceous strata, the soil densely covered with dry leaves of trees.
Clement’s and Mackenzie’s flowering photographs ( 18.XI.2006 ) Castillon’s photograph ( 17.VII.2010 ) «Nusbaumer & Ranirison 1763» «Nusbaumer & Ranirison 1763bis»
present, triangular, acute at the tips, white absent present, triangular, acute at the tips, white present, bilobed at the tips, brown and white
fused to the mid point free almost to the base fused to the mid point adnate in the basal third
lacking rows of warts, strongly upcurved sides presence of two lines of verrucose warts along length, transversally triangular, 3-lobed at the tip lacking rows of warts, strongly upcurved sides lacking rows of warts, slightly emarginate, broadly obovate-spatulate, with sides only slightly upcurved
bilobed callus of two lines of small warts from base to tip with a fleshy yellow ligule on the claw bilobed erect entire, trilobed at the tip
10-15 unknown up to 15 up to 10
white with brown in the centre white white with brown in the centre white
unknown (the whole flower was ca.12-15 mm wide) unknown up to 15 mm 5-8 mm
unknown unknown unknown unknown
D. avaratraensis D. verrucosa D. avaratraensis D. recurvata
– – D. avaratraensis D. recurvata
The most frequent species recorded together with D. recurvata in Loky-Manambato vegetation surveys include, in decreasing abundance: Marojejya insignis Humbert , Ravenea sambiranensis Jum. & H. Perrier , Dypsis nodifera Mart., Weinmanniadecora Tul. , Syzygium condensatum (Baker) Labat & G. E. Schatz , Plagioscyphus aff. louvelii Danguy & Choux and Blechnum attenuatum (Sw.) Mett. var. attenuatum . Flowering time. – December. Conservation Status. – With only one small subpopulation, included in the Loky-Manambato protected area, Didymoplexis recurvata is assigned a preliminary status of “Critically Endangered” (CR D) following the IUCN Red List Categories and Criteria ( IUCN, 2012 ). Notes. – Didymoplexis recurvata is clearly distinguished from the other African and Malagasy species of Didymoplexis known in flower by its column which has short recurved apical arms that are bilobed at the tips, as well as by its lip which lacks rows of warts but has at the base a tall apically trilobed entire callus and by its sepals and petals that are adnate in the basal third.