Dioscorea orangeana (Dioscoreaceae), a new and threatened species of edible yam from northern Madagascar
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A new species of yam (Dioscorea orangeana Wilkin) is described and illustrated. It differs from D. comorensis R.Knuth by having undulate leaf margins and a broader torus and tepals in both the male and female flowers. In female flowers of D. orangeana the floral stipe between the ovary and the torus is shorter than in D. comorensis. The tuber morphology of the species is atypical among Malagasy species in that there are several digitate lobes rather than a single tuber per growing season, although more research is needed on tuber morphology. D. orangeana is reported to be edible. It is endemic to the Forêt d’Orangea near Diego Suarez (Antsiranana) in Antsiranana Préfecture. Its conservation and sustainable use are thus matters of concern.
Keywordsconservation Dioscorea Dioscoreaceae edible Madagascar new species yams
The COLPARSYST programme provided financial support for a visit by PW to the Museum National d’Histoire Naturelle in Paris in October 2003, and the SYNTHESYS programme a further visit in October 2006; he would like to thank Leandro Leoz and all the staff of the Laboratoire de Phanerogamie for their help, especially Jean-Noel Labat and Thierry Deroin. Thanks are also due to the MADSUP programme which funded research undertaken by the Département de Biologie et Ecologie Végétales on Yams in the Antsiranana area. Jim Solomon helped to get access to specimens and Lucy Smith produced the excellent Figures. Dave Simpson’s constructive comments improved an earlier version of this manuscript. Odile Weber and Melanie Thomas translated the Latin diagnosis. Thanks are also due to Jean-Noel Labat, Nicole Crestey and Daan Ouni Msoili for collecting specimens and/or photographing Dioscorea comorensis.
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