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The threatened edible yams of the Dioscorea sambiranensis R.Knuth species complex (Dioscoreaceae): a new species and subspecies

Paul WILKIN, Annette HLADIK, Vololoniaina JEANNODA & Odile WEBER

en Adansonia 31 (2) - Pages 249-266

Published on 31 December 2009

The Dioscorea sambiranensis species complex is endemic to Northern and North-Western Madagascar. Its taxa have broad, cordate leaves with petioles roughly equal in length to the blade, lax male inflorescences with flowers on long pedicels arranged in cymules of usually five or more flowers and flat discoid floral tori. Following study of its morphological variation, two new taxa in the complex are described and illustrated. Dioscorea buckleyana Wilkin was part of a mixed taxonomic concept under the invalid name D. sambiranensis R.Knuth subsp. ambrensis H.Perrier. It is glabrous like D. pteropoda H.Perrier, but differs in petiole and leaf blade morphology (especially blade texture), pedicel length and capsule morphology. Clarification of the limits of D. sambiranensis R.Knuth revealed an undescribed subspecies, subsp. bardotiae Wilkin, which differs in leaf blade and petiole dimensions, and lacks the surface ornamentation of the ovary and capsule found in subsp. sambiranensis. The relationship of D. sambiranensis with D. namorokensis Wilkin is revealed. Keys, descriptions and a distribution map are provided for all the taxa covered, and conservation status assessments given. The latter show that all of the taxa of the complex are, or are likely to be, threatened.
Keywords :
Dioscoreaceae, Dioscorea, yams, Madagascar, endemic, edible, conservation, new species, new subspecies
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