Dioscorea howardiana, a new species in Dioscorea section Trigonobasis (Dioscoreaceae) OSWALDO TELLEZ-VALDES I AND R. GEETA 2 'Laboratorio de Recursos Naturales UBIPRO, Facultad de Estudios Superiores Iztacala UNAM, Av. de Los Barrios 1, Los Reyes Iztacala, Tlalnepantla C.P. 54090, Edo. de Mexico, Mexico; e-mail:
[email protected] 'Department of Ecology and Evolution, State University of New York, Stony Brook, NY 117945245, U.S.A.
Abstract. Dioscorea howardiana is proposed as a new species from Mexico and Central America as far south as Panama, and is described and illustrated. It most closely resembles D. liebmannii. Relationships, distribution, and ecological preferences of the new species are discussed. Key words: Central America, Dioscorea, Dioscoreaceae, Mexico, Trigonobasis. Resumen. Dioscorea howardiana se propone como una especie nueva de Mexico y Centroamerica, es descrita e ilustrada. Es semejante a D. liebmannii. Se discuten sus relaciones, su distribucion geografica y preferencias ecologicas.
Dioscorea L. (Dioscoreaceae) traditionally has been considered the most diverse genus within the family. However, the total number of species has not yet been well established; some authors, like Knuth (1924) estimated about 640 species, while others like Schubert and Al-Shehbaz and Schubert (1989) estimated up to 900 species. In the current classification all dioecious genera have been embedded into Dioscorea based on molecular and morphological studies; at the same time the number of species has been reduced to about 350-400 (Caddick et al., 2000). Mexico is one of the secondary centers of diversity for this group, together with Brazil (131 species) and Peru (66 species). Mexico has about 73 species of Dioscorea, of which approximately 65% are endemic to the country (Matuda, 1953, 1961; Schubert, 1973, 1989). The species inhabit mainly tropical and mesic habitats, and most flower during the rainy season, from June to October. Field and herbarium studies of the systematics of Dioscorea over the past 10 years have led to a better understanding of the Mexican species and to the description of several new ones (Te1lez & Schubert, 1987, 1991, 1994;
Ramirez & Tdllez, 1992; Tellez & Martinez, 1993; Te1lez, 1996, 1997a, 1997b, 2002; Tellez & Davila, 1998), including the following new species. Dioscorea howardiana O. Tellez, B.G. Schubert & R. Geeta, sp. nov. Type: Mexico. Chiapas: Mpio. Tuxtla Gutierrez, 10-12 miles northeast Tuxtla Gutierrez (5-6 miles by direct trail), selva baja verde on limestone mesa, ca: 4000 ft., 14-17 Sep 1952 (both d Y on sheet), H. S. Gentry 12166 (holotype: GH). Caulis dextrorsum volubilis. Foliorum lamina (3.5—)6-1 5(-27) x (2.7—)4.5-10(-20) cm, fere usque ad basim triloba, basi subtruncato-cordata, utrinque glabra vel infra adpresso-pilosa, 5-9- nervata, petiolo (1.3—)2.3(-7) cm. Racemi d in panicula axillari basi ramosa 3.5 -20cm longi, laxiflori, floribus singulatim pedicellatis; staminibus 3, antheris introrsis, rudimento stylino nullo. Racemi Q in paribus axillaribus vel alter forum ad florem pedicellatam singular reductus, pedunculati; perianthio 4 floribus masculinis simili, stylis distinctis, subulatis. Capsula 8 vel 11 mm, 4-6 mm, anguste oblonga vel elliptica, membranacea. Semina 4-6 x 2-3 mm lata, oblonga vel triangularia, deorsum alata. Long-trailing or climbing annual vine arising from a shallow rhizomes 5-15 cm, hypo-
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FIG. 1. Dioscorea howardiana. A. Staminate plant, habit. B. Pistillate plant, habit. C. Portion of staminate inflorescence. D. Portion of the infructescence. E—G. Staminate flower showing the perianth, bracts, pedicel, three stamens, and the filament insertion. H—I. Pistillate flower showing the perianth, ovary, and styles. J. Immature seed. (From the holotype.)
geous, conic, the base lobate-undulate or puberulent; petioles (1.3—)2.3(-7) cm, palmatiform, occasionally L-shaped, bark glabrous to minutely puberulent, purplish or light brown, inner tissue white. Stems dex- green, lineate, stout. Leaves trilobate (or trorsely twining, purple to green, lineate to the lower ones almost trifoliolate), occasulcate, essentially glabrous to minutely sionally the lobes slightly overlapping.
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Leaves (3.5—)6-15(-27) x (2.7—)4.5-20 cm, alternate; central lobe oval to oblong, abruptly acuminate, 3-nerved; lateral lobe semiovate, acute, 2- to 3-nerved, glabrous on both surfaces or sparsely appressed-pilose on the lower one, base retuse triangular to cordate. Staminate inflorescences axillary, compound, racemose, branched near the base; individual racemes 4-20cm long, loosely flowered; pedicels 3-3.5 mm long, their subtending bracts ca. 1 mm long, ovate-acute; perianth segments 1-1.5 mm long, 1-nerved, oblong, obtuse, reflexed at maturity; stamens 3, 0.3-0.5 mm long, about 1/ the length of the segments, arising from a disc at the base of the perianth, filaments with fleshy base; anthers introrse; stylar rudiment lacking. Pistillate inflorescences racemes in pairs 5-15 cm long (or with the second one reduced to a single pedicellate capsule), pedunculate with a peduncle 3-4 cm long; perianth with segments reflexed, staminodia lacking; stylar column lacking, styles 3, single, free from base, terete, thin, stigmas simple. Capsules 8-11 x 4-6 mm, narrowly oblong to elliptic, membranous, light brown to reddish at maturity, base rounded to oblique, apex obtuse; seeds 4-6 x 2-3 mm, oblong to triangular, 2 per locule, winged basally, brown-reddish, smooth. Additional specimens examined. MEXICO. CHIAPAS: 10-12 miles NE Tuxtla Gutierrez (5-6 miles by direct trail); selva baja verde on limestone mesa, ca. 4000 ft., 14-17 sep 1952, Gentry 12208 (GH); Mpio. Tonala, Pared6n, 93°45'42" W, 16°65" N, 17 sep 1947, Matuda 16924 (MEXU); Mojarra, 93°43'18" W, 16°6'30" N, 27 nov 1947, Matuda 17185 (MEXU). Mpio. Tuxtla Gutierrez, 17 km al N de Tuxtla Gutierrez, Parque Nacional Canon El Sumidero, Bosque tropical caducifolio, 14 nov 1984, Tellez et al. 7897 (MEXU); Carretera Tuxtla Gutierrez-Sumidero, bosque tropical subcaducifolio, 93°1141" W, 16°5321" N, 21 oct 1959, H.F. 16 (XAL); 17 km al NE de Tuxtla Gutierrez-Canon del Sumidero, alt. 1300m, 93°156" W, 16°5214" N, 1 oct 1984, Torres et al. 6407 (MEXU). HONDURAS. OLANCHO: 7.3 miles NE of San Francisco de la Paz, on road between San Francisco de la Paz and Gualaco, 86°12 W, 14°58' N, 5 feb 1987, Croat and Hannon 64191 (MEXU). EL SALVADOR. FRANCISCO MORAZAN: Mpio. San Antonio Oriente, 14 km al NO de Zamorano, entre La Labranza y In cima del Cerro Uyuca, 87°411" W, 14° 134" N, 1950 m, Linares 2209 (MEXU). NICARAGUA. Ca. 5.2 km N of San Fernando, Valley of rio San Fernando, 800 m, NE to Portillo Los Coyoles, altitud 1083 m, SW up narrow quebrada to cerro El
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Penascal, 1125m, 86°1930" W, 13°230" N, 10 to 13 Aug. 1977, Stevens and Krukoff 3130 (MEXU, MO). PANAMA. Duke 8808, no data (MO).
Distribution and habitat. Dioscorea howardiana inhabits mainly tropical deciduous and subdeciduous forests. Phenology. Flowering occurs from July to September, fruiting from September to March. Etymology. We dedicate this species to Howard Scott Gentry (1903-1993) who widely collected in Mexico. Dioscorea howardiana was previously misunderstood by Tellez & Schubert (1994), who treated it as D. liebmannii in their publication of the Mesoamerican species of Dioscorea. Dioscorea liebmannii is a species commonly distributed in western Mexico, in much dryer habitats than those in Mesoamerica. After reviewing the type collection of D. liebmannii (B), studying the specimens reported herein, and conducting fieldwork for a research project on the phylogeny of Dioscorea, we concluded that the collections from southern Mexico and Central America previously treated as D. liebmannii should be proposed as a new species. The known relationships of the new species are within section Trigonobasis Uline subgenus Helmia (Kunth) Benth. Within the section there is a strong tendency to develop lobed leaves, on the basis of which Knuth (1924) proposed subsection Lobatae. In this subsection, D. howardiana is close to D. cruzensis Knuth, D. galeottiana Kunth, and D. liebmannii Uline. Dioscorea howardiana may be distinguished from D. cruzensis by its staminate inflorescences with longer-pedicellate flowers at greater distances from each other along the rachis, by its stamens with filaments much enlarged toward the base and attached to a fleshy disc and bearing anthers in an erect fashion so that they do not touch each other, by it less deeply lobed leaves, and by its purple to green stems. From D. galeottiana, D. howardiana may be distinguished by the absence of a stylar rudiment in its staminate flowers and by its deeply lobed leaves; D. galeottiana also occurs at higher elevations. Finally, the new species differs from D. liebmannii because the latter has multiflowered staminate inflores-
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cences (cymes), and the flowers are much closer to each other. Among all the species, D. howardiana is the only one with regularly early-reflexed lobes in flowers of both sexes. Acknowledgments We would like to thank Dr. Patricia DavilaAranda, who critically reviewed the manuscript and suggested valuable comments and corrections, as well as two anonymous reviewers for their comments and corrections. We thank the FES Iztacala UNAM - PAPCA program (2003) for support to carry out fieldwork, CONABIO (DS001), Royal Botanic Gardens Kew (Millenium Seed Bank project), FES Iztacala for the support to review European herbaria (BR, G, K, MA, P), and the National Science Foundation (NSF-DEB-1021680) for the financial support for the phylogeny of Dioscorea project. We thank Regina O. Hughes for the excellent drawing of the species. Literature Cited Al- Shehbaz, I. & B. G. Schubert. 1989. The Dioscoreaceae in the Southeastern United States. Journal of the Arnold Arboretum 70: 57-95. Caddick, L. R., P. Wilkin, P. Rudall, T. A. J. Henderson & M. W. Chase. 2002. Yams reclassified: a recircumscription of Dioscoreaceae and Dioscoreales. Taxon 51: 103-114. Knuth, R. 1924. Dioscoreaceae. In Engler: Das Pflanzenr. IV. 43 (Heft 87): 1-387. Matuda, E. 1953. Las Dioscoreas de Mexico. Anales del Instituto de Biologia. Universidad Nacional Aut6noma de Mexico, Serie Botanica 24: 279-390. . 1961. Nuevas Plantas de Mexico. Anales del In-
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stituto de Biologia. Universidad Nacional Autonoma de Mexico, Serie Botanica 32: 143-147. Ramirez, R. R.R. & 0. Tellez V. .1992. El genero Dioscorea (Dioscoreaceae) en el estado de Morelos, Mexico. Anales del Instituto de Biologia. Universidad Nacional Autonoma de Mexico, Serie Botanica 63: 67-100. Schubert, B. G. 1973. Aspects of taxonomy in the genus Dioscorea. Publ. Especial 8. Instituto Nacional Investigaciones Forestales, Mexico, D.F. . 1989. Dioscoreaceae. In: W. R. Anderson (ed.), Flora Novo-Galiciana. A Descriptive Account of the Vascular Plants of Western Mexico. University of Michigan Herbarium 15: 355-388. Tellez, V. O. 1996. Dioscoreaceae. Flora del Valle de Tehuacan-Cuicatlan. Fasciculo 9. Instituto de Biologia UNAM. . 1997a. Additions to the Flora Mesoamericana: A new species of Dioscorea (Dioscoreaceae) from Panama. Novon 7: 208-209. . 1997b. Nomenclatural changes in Mexican Dioscoreaceae and Leguminosae. Contributions of the University of Michigan Herbarium 21: 309-313. - 2002. Una especie nueva y notas sobre una especie notable de Dioscorea (Dioscoreaceae) para Mexico. Novon 12: 411-414. & P. Davila A. 1998. Nanarepenta juxtlahuacensis (Dioscoreaceae), una especie nueva de Oaxaca, Mexico. Novon 8:210-214. & A. Martinez R. 1993. A new species of Dioscorea (Dioscoreaceae) from Mesoamerica. Novon 3: 208-210. & B. G. Schubert. 1987. Una nueva especie de Dioscorea (Dioscoreaceae) del estado de Queretaro, Mexico. Annals of the Missouri Botanical Garden 74: 539-541. & . 1991. Especies nuevas y colecciones notables de Dioscorea (Dioscoreaceae) en Mesoamerica. Annals of the Missouri Botanical Garden 78: 245-253. & . 1994. Dioscorea (Dioscoreaceae). In: Flora Mesoamericana 6: 54-65. Ed. UNAM. Mexico.
