ISSN 1346-7565 Acta Phytotax. Geobot. 71 (3): 187–199 (2020) doi: 10.18942/apg.202003 A Revised Infrageneric Classification of Old World Species of Dioscorea (Dioscoreaceae) 1,* 1 2 3 3 HIROSHI NODA , SHIZUKA FUSE , JUN YAMASHITA , RACHUN POOMA , MANOP POOPATH , 1 1 HIROSHI TOBE AND MINORU N. TAMURA 1Department of Botany, Graduate School of Science, Kyoto University, Kitashirakawa-oiwake-cho, Sakyo-ku, Kyoto 606-8502, Japan. *[email protected] (author for correspondence); 2Institute of Plant Science and Resources, Okayama University, Chuo 2-20-1, Kurashiki-shi, Okayama 710-0046, Japan; 3The Forest Herbarium, Department of National Parks, Wildlife and Plant Conservation, Chatuchak, Bangkok 10900, Thailand Dioscorea (Dioscoreaceae), a morphologically diverse genus, consists of more than 600 species distrib- uted worldwide. Recent molecular and morphological analyses allowed us to recognize two subgenera, Dioscorea and Helmia, and 19 Old World species groups (sections) in subgenus Helmia. In this paper we present a diagnostic key and taxonomic treatment for the subgenera and sections, including D. sect. Ta- mus (stat. nov.) and four new sections; Afroborderea, Perennia (validated here), Pseudoshannicorea and Pseudostenophora. Lectotype species for eleven sections; Enantiophyllum, Illigerastrum, Lasiophyton, Macrocarpaea, Macropoda, Madagascarienses, Orientali-asiaticae, Rhacodophyllum, Shannicorea, Stenophora and Syntepaleia, are also designated. Keywords: Dioscorea, Dioscorea sect. Afroborderea, Dioscorea sect. Perennia, Dioscorea sect. Pseu- doshannicorea, Dioscorea sect. Pseudostenophora, Dioscorea sect. Tamus, Dioscorea subg. Helmia, Dioscoreaceae, lectotypification, taxonomy Dioscorea (Dioscoreaceae), yams, are mostly used by combining all existing cpDNA sequence dioecious vines with twining stems (Fig. 1). data obtained in previous studies (Caddick et al. Based on their great morphological diversity, 2002a, Wilkin et al. 2005, Gao et al. 2008, Hsu et about 630 species have been recognized (WCSP al. 2013, Maurin et al. 2016, Viruel et al. 2016, 2019). Previous authors have proposed infrage- Couto et al. 2018) with our original data (Noda et neric taxa (23 to 58 sections and several subgen- al. 2020). era) and several separate genera (which were re- The resultant phylogenetic tree consisted of cently placed within Dioscorea based on molecu- eleven major clades (Fig. 2a), most of which fur- lar evidence) (Uline 1898, Knuth 1924, Burkill ther consisted of more than two strongly or mod- 1960, Huber 1998, for review see Caddick et al. erately supported subclades (Noda et al. 2020). 2002a, Noda et al. 2020). However, diagnostic As in previous studies (Wilkin et al. 2005, Viruel keys to the taxa (genera/subgenera/sections) dif- et al. 2016, 2018, Couto et al. 2018), Dioscorea fer greatly among the authors and no consensus section Stenophora was sister to the rest of the has emerged with regard to the recognition and/or genus. Using the tree in Fig. 2b, which was mod- circumscription of many of the infrageneric taxa. ified from Fig. 2a and consisted of 27 major clades To resolve this problem, we conducted phyloge- and/or final major subclades including 20 Old netic analyses of 273 samples from 183 species of World sections, we determined the evolution of Dioscorea based on four cpDNA regions, matK, ten selected morphological characters (Noda et rbcL, atpB and trnL–F (Noda et al. 2020). For the al. 2020). The Gillettii–group, Burchellii–group, phylogenetic analyses, 3,754 characters were Tentaculigera–group and Birmanica–group 188 Acta Phytotax. Geobot. Vol. 71 FIG. 1. Habit of species of Dioscorea. a. D. tokoro (staminate); b. D. tentaculigera (staminate); c. D. bulbifera (staminate); d. D. esquirolii (sterile); e. D. velutipes (pistillate); f. D. japonica (staminate). October 2020 NODA & AL. — An Infrageneric Classification of Old World Dioscorea 189 TABLE 1. Data matrix of ten morphological characters in Mesquite of sections and species groups of Dioscorea. Sections and species groups [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] Dioscorea 0 0 0 0 0&1 0 0 0&1 0&1 1&0 NWI (Epipetrum) 1 1 2 0 0 2 0 0 0 4 NWI (expect Epipetrum) 1 1 1 0 0&1 0 0 0 0 1&0 NWII 1 0&1 1 0 0 1 0 0 0 1 Borderea 1 0 3 0 0 2 0 0 0 4 Tamus 1 1 3 1 0 0 0 ? 0 4 Afoborderea 1 1 ? 0 0 0 0 0 0 4 Rhacodophyllum 1 1 ? 0 0 0 0 0 0 0 Perennia 1 1 ? 0 0 0 0 0 0 1 Testudinaria 1 1 0 0 0 0&2 0 0 0 2 Pseudoshannicorea 1 ? 4 0 0 0 0 0 0 3 Opsophyton 1 1 4 0 0 0 0 0 0 1 Lasiophyron 1 1 4 0 1 0 0 0 1 1 NWIII (Apodostemon2) 1 ? ? 0 0 0 0 0 0 0 NWIII (Lasiogyne) 1 1 4(&1) 0 0 0 0 1 0 0 NWIII (Apodostemon1) 1 1 4(&1) 0 0 0 0 0 0 0 NWIII (Rajania) 1 ? ? 2 0 0 0 ? 0 4 Macroura 1 1 4 0 0 0 1 0 0 3 Cardiocarpa 1 1 ? 0 0&1 0 0 1 0 0 Brachyandra 1 1 ? 0 0 0 0 0 0 1 Stenocorea 1 1 ? 0 0 0 0 1 0 0 Combilium 1 1 4 0 0 0 0 0 1 0 Shannicorea 1 1 4 0 0 0 0 0 1 2 Paramecocarpa 1 ? ? 0 0 0 0 0 1 2 Macrocarpaea 1 1 4 0 0 0 0 0 1 3 Pseudostenophora 0 1 ? 0 0 0 0 1 1 0 Enantiophyllum 1 1 4 0 0 1 1 1 0&1 0&2 Characters and character-states. [1] Underground stem rhizome (0), tuber (1); [2] number of pollen aperture monosulcate (0), bisulcate (1); [3] chromosome: x = 10 and diploid (0), x = 9 (1), x = 7 (2), x = 6 (3), polyploid of x = 10 (4); [4] fruit: capsule (0), berry (1), samara (2); [5] leaf: simple (0), compound (1); [6] stem: twining to left (0), twining to right (1) or not twinned (2); [7] phyllotaxis alternate (0), opposite (1); [8] capsule longer than its width (0) or wider than its length (1); [9] stem/leaf indu- mentum absent (0) or present (1); [10] seed wings all around the seed entity (0), basally (1), apically (2), or both basally and apically (3), absence of a wing (4). (Noda et al. 2020: Figs. 5 and 6) are now replaced and morphological evidence, we propose the rec- with four new sections, Dioscorea sects. Afrobor- ognition of two subgenera, Dioscorea (= D. sect. derea, Perennia, Pseudoshannicorea, and Pseu- Stenophora) and Helmia, as well as the need for a dostenophora (described below). The morpholog- revision of the infrageneric classification of the ical characters we analyzed include not only Old World species in subgenus Helmia (Noda et those used in previous infrageneric classifica- al. 2020). tions (Uline 1897, 1898, Knuth 1924, Burkill In this paper, we present a diagnostic key and 1960, Huber 1998), but also pollen and chromo- taxonomic treatment for the two subgenera and some characters, whose systematic and evolu- the 20 Old World sections, of which 19 belong to tionary implications have been suggested for the subgenus Helmia. Of the 20 Old World sections, past 40 years (Pei et al. 1979, Chin et al. 1985, the following 13 have already been proposed and Schols et al. 2005, Viruel et al. 2010). The ten properly circumscribed, mostly by Huber (1998) characters and distribution of their respective as genera or genus-equivalent sections. They are character states are shown in Table 1 (see also Ta- Borderea, Brachyandra, Combilium, Dioscorea ble 2 in Noda et al. 2020). Based on molecular [= D. sect. Stenophora Uline circumscribed by 190 Acta Phytotax. Geobot. Vol. 71 <50 Dioscorea japonica* <50 <50 D. tabatae 6(1) 7(1)10(0&2) <50 D. japonica <50 D. potaninii 77 D. doryphora 62 52 D. japonica 57 D. polystachya & D. batatas 73 D. polystachya 74 62 76 60 D. polystachya* 61 D. cirrhosa* 8(1) 78 62 Enantiophyllum 53 D. formosana <50 66 76 60 D. matsudae <50 64 D. cirrhosa D. cirrhosa 90 98 64 D. benthamii* 96 D. pseudojaponica 60 67 D. glabra* 78 72 D. fordii 10(0) 89 D. nummularia 87 D. lepcharum 86 D. calcicpla 95 89 91 89 D. alata* 86 89 D. fordii <50 D. oryzetorum D. inoponata 73 Pseudostenophora** 81 D. exalata* 88 98 52 D. brevipetiolata 58 94 D. hamiltonii 100 61 100 D. wallichii* 93 D. aspersa D. kratica 99 D. nummularia 96 67 91 D. elegans 53 51 <50 D. hastifolia ⑪96 D. minutiflora 58 52 D. luzonensis 98 D. decipiens 60 D. lanata 99 96 88 98 D. cotinifolia* 94 89 D. schimperiana* 9 10(2) Shannicorea* D. birmanica 90 D. martini 73 95 D. nitens 68 D. velutipes 67 D. yunnanensis 73 92 80 94 D. subcalva var. submollis* 90 88 86 D. subcalva* 100 ⑩ 95 99 D. pseudonitens* 99 72 86 D. nitens 94 D. velutipes 91 87 89 D. hemsleyi* 88 100 99 D. petelotii* 80 D. preussii 90 ⑨ 81 98 D. esculenta* 73 D. daunaea Paramecocarpa* <50 D. ovinala 88 D. namorokensis 87 74 78 D. soso 67 D. mayottensis 72 D. hombuka 76 D. madecassa 91 D. alatipes 99 <50 D. maciba 10(3) 100 69 D. hexagona 99 D. trichantha 98 D. fandra 83 80 99 D. arcuatinervis 94 D. bemarivensis <50 100 100 D. sansibarensis* 70 <50 D. cordata (Rajania) Macrocarpaea* ⑧<50 100 D. hyalinomarginata (Rajania) 83 100 <50 D. baracoensis (Rajania) OW D. scorpioidea (Rajania) 100 74 D. trifida 98 <50 <50 D. dodecaneura D. stegelmanniana 94 73 83 D. pentaphylla* 76 <50 D. esquirolii <50 D. tomentosa 89 D.