Dioscorea

Dioscorea is a genus of over 600 species of flowering plants in the family Dioscoreaceae, native throughout the tropical and warm temperate regions of the world. The vast majority of the species are tropical, with only a few species extending into temperate climates.Govaerts, R., Wilkin, P. & Saunders, R.M.K. (2007). World Checklist of Dioscoreales. Yams and their allies: 1-65. The Board of Trustees of the Royal Botanic Gardens, Kew.Wilkin, P. & Thapyai, C. (2009). Flora of Thailand 10(1): 1-140. The Forest Herbarium, National Park, Wildlife and Plant Conservation Department, Bangkok. It was named by the monk Charles Plumier after the ancient Greek physician and botanist Dioscorides.

Description They are tuberous herbaceous perennial lianas, growing to or more tall. The leaves are spirally arranged, mostly broad heart-shaped. The flowers are individually inconspicuous, greenish-yellow, with six petals; they are mostly dioecious, with separate male and female plants, though a few species are monoecious, with male and female flowers on the same plant. The fruit is a capsule in most species, a soft berry in a few species.

Most Dioscorea species that have been examined possess extrafloral nectaries at the petiole or leaf underside.

Cultivation and uses Several species, known as yams, are important agricultural crops in tropical regions, grown for their large tubers. Many of these are toxic when fresh, but can be detoxified and eaten, and are particularly important in parts of Africa, Asia, and Oceania.

One class of toxins found in many species is steroidal saponins, which can be converted through a series of chemical reactions into steroid hormones for use in medicine and as contraceptives.

The 1889 book "The Useful Native Plants of Australia" records that Dioscorea hastifolia is "One of the hardiest of the yams. The tubers are largely consumed by the local aborigines for food. (Mueller)."

Evolution The earliest known fossil Dioscorea are D. lindgrenii & D. shermani, both of which are known from fossil fruit from the Early Eocene-aged Green River Formation of Wyoming, US. It has been suggested that Dioscorea likely originated in North America around this time period, as no evidence of Dioscorea fossils is known from Paleocene deposits in South America despite that region having among the highest Dioscorea diversity in the modern day. Another early Dioscorea species is D. eocenicus, known from fossil leaves from the Early Eocene-aged Palana Formation of Rajasthan, India.

Accepted species, subspecies, and varieties

The genus includes the following species and subspecies:

A

Dioscorea abysmophila Maguire & Steyerm. Dioscorea abyssinica Hochst. ex Kunth Dioscorea acanthogene Rusby Dioscorea acerifolia Phil. Dioscorea acuminata Baker Dioscorea adenantha Uline Dioscorea aesculifolia R.Knuth Dioscorea aguilarii Standl. & Steyerm. Dioscorea alata L. Dioscorea alatipes Burkill & H.Perrier Dioscorea althaeoides R.Knuth Dioscorea altissima Lam. Dioscorea amaranthoides C.Presl Dioscorea amazonum Mart. ex Griseb. Dioscorea amazonum var. klugii (R.Knuth) Ayala Dioscorea amoena R.Knuth Dioscorea analalavensis Jum. & H.Perrier Dioscorea ancachsensis R.Knuth Dioscorea andina Phil. Dioscorea andromedusae O.Téllez Dioscorea angustifolia Rusby Dioscorea anomala Griseb. Dioscorea antaly Jum. & H.Perrier Dioscorea antucoana Uline ex R.Knuth Dioscorea arachidna Prain & Burkill Dioscorea araucana Phil. Dioscorea arcuatinervis Hochr. Dioscorea argyrogyna Uline ex R.Knuth Dioscorea arifolia C.Presl Dioscorea aristolochiifolia Poepp. Dioscorea arnensis R. Knuth Dioscorea asclepiadea Prain & Burkill Dioscorea aspera Humb. & Bonpl. ex Willd. Dioscorea aspersa Prain & Burkill Dioscorea asperula Pedralli Dioscorea asteriscus Burkill Dioscorea atrescens R.Knuth Dioscorea auriculata Poepp.

B

Dioscorea bahiensis R.Knuth Dioscorea bako Wilkin Dioscorea balakrishnanii Dioscorea balcanica Košanin Dioscorea bancana Prain & Burkill Dioscorea banzhuana S.J.Pei & C.T.Ting Dioscorea bartlettii C.V.Morton Dioscorea basiclavicaulis Rizzini & A.Mattos Dioscorea baya De Wild. Dioscorea beecheyi R.Knuth Dioscorea belophylla (Prain) Voigt ex Haines Dioscorea bemandry Jum. & H.Perrier Dioscorea bemarivensis Jum. & H.Perrier Dioscorea benthamii Prain & Burkill Dioscorea berenicea McVaugh Dioscorea bermejensis R.Knuth Dioscorea bernoulliana Prain & Burkill Dioscorea besseriana Kunth Dioscorea beyrichii R.Knuth Dioscorea bicolor Prain & Burkill Dioscorea biformifolia S.J.Pei & C.T.Ting Dioscorea biloba (Phil.) Caddick & Wilkin Dioscorea biplicata R.Knuth Dioscorea birmanica Prain & Burkill Dioscorea birschelii Harms ex R.Knuth Dioscorea blumei Prain & Burkill Dioscorea bolivarensis Steyerm. Dioscorea bonii Prain & Burkill Dioscorea bosseri Haigh & Wilkin Dioscorea brachybotrya Poepp. Dioscorea brachystachya Phil. Dioscorea bradei R.Knuth Dioscorea brandisii Prain & Burkill Dioscorea brevipetiolata Prain & Burkill Dioscorea bridgesii Griseb. ex Kunth Dioscorea brownii Schinz Dioscorea bryoniifolia Poepp. Dioscorea buchananii Benth. Dioscorea buckleyana Wilkin Dioscorea bulbifera L. Dioscorea bulbotricha Hand.-Mazz. Dioscorea burchellii Baker Dioscorea burkilliana J.Miège

C

Dioscorea cachipuertensis Ayala Dioscorea calcicola Prain & Burkill Dioscorea caldasensis R.Knuth Dioscorea calderillensis R.Knuth Dioscorea callacatensis R.Knuth Dioscorea cambodiana Prain & Burkill Dioscorea campanulata Uline ex R.Knuth Dioscorea campestris Griseb. Dioscorea campos-portoi R.Knuth Dioscorea carionis Prain & Burkill Dioscorea carpomaculata O.Téllez & B.G.Schub. Dioscorea carpomaculata var. cinerea (Uline ex R.Knuth) O.Téllez & B.G.Schub. Dioscorea castilloniana Hauman Dioscorea catharinensis R.Knuth Dioscorea caucasica Lipsky Dioscorea cavenensis Lam. Dioscorea cayennensis Lam. Dioscorea cayennensis subsp. rotundata (Poir.) J.Miège; syn.: D. rotundata Poir. Dioscorea ceratandra Uline ex R.Knuth Dioscorea chacoensis R.Knuth Dioscorea chagllaensis R.Knuth Dioscorea chancayensis R.Knuth Dioscorea chaponensis R.Knuth Dioscorea chiapasensis Matuda Dioscorea chimborazensis R.Knuth Dioscorea chingii Prain & Burkill Dioscorea choriandra Uline ex R.Knuth Dioscorea chouardii Gaussen Dioscorea cienegensis R.Knuth Dioscorea cinnamomifolia Hook. Dioscorea cirrhosa Lour. Dioscorea cissophylla Phil. Dioscorea claessensii De Wild. Dioscorea claussenii Uline ex R.Knuth Dioscorea claytonii Ayala Dioscorea cochleariapiculata De Wild. Dioscorea collettii Hook.f. Dioscorea collettii var. hypoglauca (Palib.) S.J.Pei & C.T.Ting Dioscorea communis (L.) Caddick & Wilkin Dioscorea commutata R.Knuth Dioscorea comorensis R.Knuth Dioscorea composita Hemsl. Dioscorea contracta R.Knuth Dioscorea convolvulacea Cham. & Schltdl. Dioscorea convolvulacea subsp. grandifolia (Schltdl.) Uline ex R.Knuth Dioscorea conzattii R.Knuth Dioscorea cordifolia Laness. Dioscorea coreana (Prain & Burkill) R.Knuth Dioscorea coriacea Humb. & Bonpl. ex Willd. Dioscorea coripatenis J.F.Macbr. Dioscorea coronata Hauman Dioscorea cotinifolia Kunth Dioscorea craibiana Prain & Burkill Dioscorea crateriflora R.Knuth Dioscorea crotalariifolia Uline Dioscorea cruzensis R.Knuth Dioscorea cubensis R.Knuth Dioscorea cumingii Prain & Burkill Dioscorea curitybensis R.Knuth Dioscorea cuspidata Humb. & Bonpl. ex Willd. Dioscorea cuyabensis R.Knuth Dioscorea cyanisticta J.D.Sm. Dioscorea cymosula Hemsl. Dioscorea cyphocarpa C.B.Rob. ex Knuth

D

Dioscorea daunea Prain & Burkill Dioscorea davidsei O.Téllez Dioscorea de-mourae Uline ex R.Knuth Dioscorea debilis Uline ex R.Knuth Dioscorea decaryana H.Perrier Dioscorea decipiens Hook.f. Dioscorea decorticans C.Presl Dioscorea deflexa Griseb. Dioscorea delavayi Franch. Dioscorea delicata R.Knuth Dioscorea deltoidea Wall. ex Griseb. Dioscorea dendrotricha Uline Dioscorea densiflora Hemsl. Dioscorea depauperata Prain & Burkill Dioscorea diamantinensis R.Knuth Dioscorea dicranandra Donn.Sm. Dioscorea dielsii R.Knuth Dioscorea dissimulans Prain & Burkill Dioscorea divaricata Blanco Dioscorea diversifolia Griseb. Dioscorea dodecaneura Vell. Dioscorea dregeana (Kunth) T.Durand & Schinz Dioscorea duchassaingii R.Knuth Dioscorea dugesii C.B.Rob. Dioscorea dumetorum (Kunth) Pax Dioscorea dumetosa Uline ex R.Knuth

E

Dioscorea ekmanii R.Knuth Dioscorea elegans Ridl. ex Prain & Burkill Dioscorea elephantipes (L'Hér.) Engl. Dioscorea entomophila Hauman Dioscorea epistephioides Taub. Dioscorea escuintlensis Matuda Dioscorea esculenta (Lour.) Burkill Dioscorea esquirolii Prain & Burkill Dioscorea exalata C.T.Ting & M.C.Chang

F

Dioscorea fandra H.Perrier Dioscorea fasciculocongesta (Sosa & B.G.Schub.) O.Téllez Dioscorea fastigiata Gay Dioscorea fendleri R.Knuth Dioscorea ferreyrae Ayala Dioscorea filiformis Blume Dioscorea flabellifolia Prain & Burkill Dioscorea flaccida R.Knuth Dioscorea floribunda M.Martens & Galeotti Dioscorea floridana Bartlett Dioscorea fodinarum Kunth Dioscorea fordii Prain & Burkill Dioscorea formosana R.Knuth Dioscorea fractiflexa R.Knuth Dioscorea fuliginosa R.Knuth Dioscorea furcata Griseb. Dioscorea futschauensis Uline ex R.Knuth

G

Dioscorea galeottiana Kunth Dioscorea galiiflora R.Knuth Dioscorea gallegosi Matuda Dioscorea garrettii Prain & Burkill Dioscorea gaumeri R.Knuth Dioscorea gentryi O.Téllez Dioscorea gillettii Milne-Redh. Dioscorea glabra Roxb. Dioscorea glandulosa (Griseb.) Klotzsch ex Kunth Dioscorea glandulosa var. calcensis (R.Knuth) Ayala Dioscorea glomerulata Hauman Dioscorea gomez-pompae O.Téllez Dioscorea gracilicaulis R.Knuth Dioscorea gracilipes Prain & Burkill Dioscorea gracilis Hook. ex Poepp. Dioscorea gracillima Miq. Dioscorea grandiflora Mart. ex Griseb. Dioscorea grandis R.Knuth Dioscorea grata Prain & Burkill Dioscorea gribinguiensis Baudon Dioscorea grisebachii Kunth Dioscorea guerrerensis R.Knuth Dioscorea guianensis R.Knuth

H

Dioscorea haenkeana C.Presl Dioscorea hamiltonii Hook.f. Dioscorea hassleriana Chodat Dioscorea hastata Mill. Dioscorea hastatissima Rusby Dioscorea hastifolia Nees Dioscorea hastiformis R.Knuth Dioscorea haumanii Xifreda Dioscorea havilandii Prain & Burkill Dioscorea hebridensis R.Knuth Dioscorea hemicrypta Burkill Dioscorea hemsleyi Prain & Burkill Dioscorea heptaneura Vell. Dioscorea herbert-smithii Rusby Dioscorea herzogii R.Knuth Dioscorea heteropoda Baker Dioscorea hexagona Baker Dioscorea hieronymi Uline ex R.Knuth Dioscorea hintonii R.Knuth Dioscorea hirtiflora Benth. Dioscorea hirtiflora subsp. orientalis Milne-Redh. Dioscorea hispida Dennst. Dioscorea holmioidea Maury Dioscorea hombuka H.Perrier Dioscorea hondurensis R.Knuth Dioscorea howardiana O.Téllez, B.G.Schub. & Geeta Dioscorea humifusa Poepp. Dioscorea humilis Bertero ex Colla Dioscorea humilis subsp. polyanthes (F.Phil.) Viruel, Segarra & Villar Dioscorea hunzikeri Xifreda

I

Dioscorea igualamontana Matuda Dioscorea incayensis R.Knuth Dioscorea inopinata Prain & Burkill Dioscorea insignis C.V.Morton & B.G.Schub. Dioscorea intermedia Thwaites Dioscorea ionophylla Uline ex R.Knuth Dioscorea iquitosensis R.Knuth Dioscorea irupanensis R.Knuth Dioscorea itapirensis R.Knuth Dioscorea itatiensis R.Knuth

J

Dioscorea jaliscana S.Watson Dioscorea jamesonii R.Knuth Dioscorea japonica Thunb. - Shan yao in Chinese () Dioscorea javariensis Ayala Dioscorea juxtlahuacensis (O.Téllez & Dávila) Caddick & Wilkin

K

Dioscorea kalkapershadii Prain & Burkill Dioscorea kamoonensis Kunth Dioscorea keduensis Burkill ex Backer Dioscorea kerrii Prain & Burkill Dioscorea killipii R.Knuth Dioscorea kimiae Wilkin Dioscorea kingii R.Knuth Dioscorea kituiensis Wilkin & Muasya Dioscorea kjellbergii R.Knuth Dioscorea knuthiana De Wild.