Dioscorea campestris Kunth ex Pedralli. 2004

Couto, Ricardo S., Tenorio, Vitor, Alzer, Fernanda da C., Lopes, Rosana C., Vieira, Ricardo C., Mendonça, Cláudia B. F., Gonçalves-Esteves, Vania & Braga, João Marcelo Alvarenga, 2014, Taxonomic Revision of the Dioscorea campestris Species Assemblage (Dioscoreaceae), Systematic Botany (Basel, Switzerland) 39 (4), pp. 1056-1069 : 1059-1064

Dioscorea campestris Kunth ex Pedralli. 2004 . Diosocoreáceas. Pp. 36 in Flora ilustrada Catarinense, fasc. Diosc., ed. R. Reitz, “pro syn.”

Left-twining vine, perennial, dioecious ( Figs. 3E ; 4A ). Tuber discoid to lobed, with only one meristematic point to which the aerial stem is attached, with many fine roots emerging from edge of the tuber, periderm brown–grayish, parenchyma yellowish–white, ca. 15 cm below the soil surface ( Figs. 3L–M ; 4B–C ). Stems to at least 2.5 m long, initially erect to twining, glabrous, terete, unarmed, green, herbaceous, 2 mm diam. at base; cataphylls present towards stem base, rather brittle, lanceolate, lateral nodal flanges and bulbils not present, 0.5 –1 mm diam. on apical shoots. Leaves alternate, entire, monomorphous; petiole 0.4–2 cm long, with short basal and apical pulvini, twisted at base, flat to slightly canaliculate, glabrous; blade 5–12 + 1.2–5 cm, dark green above and bright green below, glabrous on both sides, chartaceous, ovate to narrowly elliptic, with very narrow sinus 1–4 mm deep, base cordate with rounded lobes, apex acuminate, bearing an acuminate forerunner tip 0.8 –2.1 mm long, protruding veins 3–7 below. Staminate inflorescence 6.5–25 cm long, initially erect, becoming pendent, one per axil, heterothetic compound inflorescence with racemes on principal axis and drepanium on secondary axis, 1–7 flowers per rachis node, bracts present at pedicel base and at drepanium base and branching points. Staminate flowers pedicellate, floral bracts 0.8–1.3 + 0.3–0.6 mm, ovate to lanceolate, membranous, torus deeply convex, perianth light green, slightly campanulate, lobes reflexed, inner and outer tepals 1.5 –2 + 1 –1.4 mm, oblong to obovate, glabrous, with fine midrib; stamens six, inserted at base of perianth segments, exserted, filaments ca. 2 mm long, free, anthers ca. 0.3 mm long, pistillodes inconspicuous ( Figs. 3A –D ; 4D ). Pistillate inflorescence 2– 8.6 cm long, simple, spicate, pendent, one per axil, 1 or 2 bracts at pedicel base. Pistillate flowers sessile, one per rachis node, floral bracts 1.5 –2 + 0.3 –0.6 mm, oblong to ovate– acuminate, torus shallowly convex, perianth yellowish to light brown, campanulate, internal and external tepals 1–1.5 + 0.6–0.8 mm, ovate–acuminate, glabrous, with fine midrib; gynoecium tricarpellate, styles 3, fused to form a 1 mm long, stout, erect, cylindrical column, 3-lobed at apex, each lobe recurved and splitting into two, stigmatic surfaces flat; staminodes six, ca. 1 mm long, antheriform; ovary dark green, glabrous ( Figs. 3F–I ; 4E ). Capsules 1.6– 1.9 + 0.8 –1 cm, dark brown to whitish, oblong to elliptic, initially pendent, reflexing during maturation to erect positions, valves chartaceous when mature, opening from ca. ⅓ to ⅔ of their length, glabrous, perianth traces at apex, margin dilated; seeds 0.6 –0.8 cm long, dark brown, oblong, wing 1.3– 1.6 + 0.6– 0.9 mm, elongated to seed base ( Figs. 3J–K ; 4F ).

Anatomy— The aerial stem has a uniseriate epidermis with a thick cuticle. Angular collenchyma constitutes about three cell layers, while the rest of the cortex is composed of parenchyma cells. An endodermoid layer has parenchyma cells with lignified walls. The central cylinder has a peripheral fibrous ring. The vasculature consists of three common vascular bundles and three cauline vascular bundles ( Fig. 2A ). Both types of vascular bundles have one pair of large vessels and two to three phloem units; the pith is extremely reduced and strongly sclerified ( Fig. 2A ).

Storied cork with approximately three layers of brachysclereids covers the tuber ( Fig. 2C ).

Palynology— Small (20.5 Mm) ( Tables 2, 3), heteropolar ( Fig. 1A ), in monads, amb elliptic, monocolpate with long and wide colpi (ca. 17.2 + 4.0 Mm) with thick edges ( Fig. 1A ), psilate. Ornamentation reticulate, heterobrochate ( Fig. 1A– B ); columellae simple, with low muri and sparse perforations ( Fig. 1A– B ), with granules within the lumen and lumina of generally uniform sizes ( Fig. 1B ). Sexine (ca. 1.0 Mm) almost as thick as the nexine (ca. 0.9 Mm).

Distribution and Ecological Data— Distributed in Argentina, Brazil, and Paraguay, being found from Amazonas State in Brazil to Buenos Aires Province in Argentina ( Fig. 5 ). This species inhabits dry to fairly moist locations, such as rocky outcrops, the edges of evergreen rainforests, grasslands, gallery forests, and rocky fields at lower altitudes (maximum of 1,800 m above sea level (masl)).

Variations could be observed in the sizes of the leaves and inflorescences, often related to the ages of the individuals, ambient humidity, or insolation. Large variations in the shapes of the leaves are uncommon, but when these occur they are usually associated with the positions of the leaves on the stem (apex–base). In the case of the Dioscorea campestris assemblage, variations observed in leaves and inflorescences were not the main motivating factor for describing the taxa treated here as synonyms, as can be seen in the treatment by Knuth (1924).

Conservation Status— Least concern (LC), as the species is widely distributed, with a continuous area of occupation. It is found in several legally protected areas in Argentina, Brazil, and Paraguay.

Phenological Data— Plants flowering from November to March, with fruits being present from November to April.

Etymology— The specific epithet comes from the Latin “campestris ”, meaning from the field, in reference to the type locality in the high altitude fields of Minas Gerais State, Brazil.

Representative Specimens Examined— ARGENTINA. Corrientes: Dept. Santo Tomé, Potrero Luna (28 21 0 S, 55 47 0 W), 5 Dec 1981, S. G. Tressens et al. 1630 ( CTES) ; Missiones: Missiones, Dep. Iguazú , Ruta 101, 11 Jan 1972, A. Nandú & L. Mrogiaski 315 ( RB) ; Dept. Concepción, Ruta 2, 16 km NE de Azara, 4 Feb 1982, A. Schinini et al. 21841 ( CTES) ; Salta: Rivadavbia, Los Blancos, Barrio Mataco (23 36 0 S, 62 35 0 W), 24 Jan 1983, A. Maranta & P. Arenas 177 ( NY) .

BRAZIL. Alagoas: Pão de Açúcar, Mata da Onça, (9 44 0 2 00 S, 37 34 0 35 00 W), 04 May 2002, R. P. Lyra-Lemos et al. 6673 ( HUEFS). Bahia: Bom Jesus da Lapa , rio São Francisco , 15 Apr 1980, R. Harley 21369 ( K, RB). Ceará: Jaguaretama , 03 May 1984, M. C. Pinheiro 153 ( R). Distrito Federal: Brasília , 21 Aug 1973, E. P. Heringer 12869a ( HB). Minas Gerais: Serra da Grão Mongol , 12 Nov 1938, F. Markgrat et al. 3476 ( RB) ; Lima Duarte, Parque Estadual do Ibitipoca , 23 Jan 2007, R. C. Forzza 4384 ( RB). Paraná: Guarapuava, Canta Galo, 01 Feb 1985, G. Hatschbach & A. C. Cervi 48877 ( PEL). Pernambuco: Custódia, Reservatório Bagres, Lote 10 (08 20 0 06.00 00 S, 037 46 0 58.80 00 W), 14 Ago 2011, R. S. Couto 531 ( HVASF) ; Alagoa de baixo, 30 Mar 1991, H. Monteiro 350 ( RBR). Rio de Janeiro: Itatiaia, Macieiras , 26 Feb 1945, A. C. Brade 17508 ( RB) ; Itatiaia, Lote 28 – 30, 5 Feb 1948, A. C. Brade 18821 ( COL, RB) ; Teresópolis, Parque Nacional da Serra dos Órgãos , trilha para a Pedra do Sino , 31 Mar 2010, R. S. Couto et al. 315 ( R, RB, RFA) ; São Fidelis, estrada para Ayres sentido Santa Maria Madalena , 28 Ago 2009, R. S. Couto et al. 232 ( R, RB, RFA) ; São Fidelis, estrada para Ayres sentido Santa Maria Madalena , 28 Ago 2009, R. S. Couto et al. 233 ( RB, RFA) ; Parque Nacional do Itatiaia, trilha para a Cachoeira Poranga , 20 Jul 2010, R. S. Couto 375 ( RB, RFA). Rio Grande do Sul: Vila Olivia para Caxias, 28 Jul 1954, B. Rambo s. n. ( PACA 31292 ) ; General Câmara, Santo Amaro, 08 Jan 1978, J. L. Waechter 703 ( ICN). Santa Catarina: Lages, 25 Dec 1956, J. Mattos s. n. ( PACA 61063 ). São Paulo: Fernandópolis, Mata do Zoológico , 10 Jun 1993, R. N. Damasceno 223 ( RB, RUSU) ; Salesópolis , 22 Nov 1957, M. Kuhlmann 4287 ( SPF) .

PARAGUAY. Alto Paraguay: Mayor Pablo Lagerenza , 16 Apr 1978, A. Schinini & E. Bordas 14986 ( CTES) ; Paraguay: Cerro Santo Tomás , Dec 1971, A. Schinini 4212 ( CTES) .

Notes— Dioscorea campestris , with two varieties, was described by Grisebach (1842) based on Martius 40 ( M) and 39 ( M), and Sellow 50 ( B, K, and P), all of which were collected in Minas Gerais State. The materials cited by Grisebach (1842) have no collection numbers (like most other Dioscorea species described by him), but by examining the types deposited in B, M, and P it was possible to encounter labels with collection number designations in the handwriting of the collectors (Sellow and Martius ), as well as the identification of D. campestris in the handwriting of Grisebach. Pedralli (2002, 2004) proposed the lectotypification of Martius s. n. ( M 175806). Upon close examination, we found that all of the syntypes perfectly matched the description of Grisebach (1842) for D. campestris .

Dioscorea campestris var. grandiflora and D. campestris var. parviflora ( Grisebach 1842) were described without any indication of the holotype material. Pedralli (2004) defined them as “nomen nudum”, and justified this proposal based on the lack of indication of the type materials. The present work accepts them as validly published based on Art. 37.1 ( McNeill et al. 2012), and we here propose lectotypification of the collection Sellow 50 (K) for Dioscorea campestris var. grandiflora and the collection Martius 40 (M) for D. campestris var. parviflora , as they best represent the characteristics described by Grisebach (1842), and are better preserved. However, we do question the morphological criteria presented by Grisebach (1842) for distinguishing the varieties. We observed substantial morphological variability in the vegetative and sexual organs of D. campestris , but without any obvious patterns that would allow the recognition of infraspecific taxa, especially those designated by Grisebach (1842) for these two varieties (based on flower size and pedicel length). Therefore, these two varieties are considered here as synonyms of D. campestris .

The new combination Helmia campestris was proposed by Kunth (1850) based on D. campestris ( Grisebach 1842) . We consider the genus Helmia to be artificial and not worthy of recognition, as noted previously by Grisebach (1875), Uline (1897), Knuth (1917, 1924), Burkill (1960), Waitt (1963), Barroso et al. (1974), Xifreda (1989), Al–Shehbaz and Schubert (1989), and Caddick et al. (2002), among others. In their phylogenetic study, Wilkin et al. (2005) likewise demonstrated that the morphological seed characters on which Helmia was based (seed wing elongate to base) had multiple origins within Dioscorea , indicating this genus as paraphyletic.

Dioscorea campestris var. longispicata was described by Hauman (1916) based on Spegazzini 20711 (BR) and 18564 (BR), and Rodriguez 325 (BR). All three specimens were collected in the Misiones Province in Argentina, but without any indication of the holotype. Pedralli (1998) indicated Spegazzini 20711 as the lectotype in his thesis, but this was not a valid publication. Pedralli (2004) later proposed subsuming this variety within D. campestris , but without validating the lectotypification. We have chosen Spegazzini 20711 as the lectotype, as it best represents the characteristics described by Hauman (1916) and is well-preserved.

Dioscorea campestris f. plantaginifolia was described by Knuth (1917) based on Schwacke 9032 (B) collected in Itacolomi, Brazil, and on Ule 3763 (B) from Itatiaia, Brazil. Subsequently, a new description for the form was presented by Knuth (1924), together with morphological data indicating the holotype as Schwacke 9032 (B). After analyzing the types, we determined that D. campestris f. plantaginifolia shows no significant morphological differences from D. campestris .

Dioscorea campestris f. stenorachis was described by Knuth (1917) based on Glaziou 14351, collected in Petrópolis, Brazil. Knuth (1924) added the collection Miers 4149 to the examined material and designated Glaziou 14351 (deposited in B) as the holotype. This material could not be found in B, however, probably having been destroyed in 1943. Pedralli (1998) wrongly designated Miers 4149 as the holotype. After analyzing Glaziou 14351 (C, G, and P) it was determined that D. campestris f. stenorachis is a synonym of D. campestris , as the main feature used by Knuth (1917) to describe the new form (staminate inflorescences two times longer than D. campestris ) can be observed in Glaziou 14351 (C, G, and P). Additionally, the D. campestris material examined had staminate inflorescences ranging from 6.5 cm (as described for D. campestris by Grisebach [1842]) to 25 cm (as described by Knuth [1924] for D. campestris f. stenorachis ). After analyzing the isotypes (C, G, and P), we here designate the collection Glaziou 14351, deposited in P (P00748327), as the lectotype as it perfectly represents the characters described by Knuth (1917) and is in better condition than the others.

Dioscorea campestris f. piedadensis was described by Knuth (1917) based on Warming s. n. collected in Serra de Piedade, Brazil. Knuth (1924) subsequently indicated Warming s. n. (deposited in B) as the holotype in his revision of Dioscoreaceae . However, this material is not in the Berlin herbarium (B) and was probably destroyed during the bombings of 1943. In examining the isotype (C), it was concluded that no morphological differences exist when compared to D. campestris and, due to the destruction/disappearance of the holotype, we here designate Warming s. n. (C10010728) as the lectotype.

Knuth (1926) proposed Dioscorea campestris f. paraguayensis based on Anisits s. n. (B 100250036) from Paraguay. The main argument used by this author to establish the new form was the morphological differences of its leaves. However, examination of the holotype (B) showed that its floral traits coincided with those of D. campestris and that the differences observed between their leaves are consistent with existing morphological variation in this species.

Dioscorea campestris Kunth was a synonym proposed by Pedralli (2004) for the species D. campestris . Pedralli (2004) justified this proposal by claiming that this taxon was a superfluous name according to Article 52 ( McNeill et al. 2012). However, when considering the publication of Kunth (1850), only Helmia campestris (Griseb.) Kunth was described, a validly published combination. The name D. campestris Kunth was not mentioned anywhere by Kunth (1850). Therefore, the proposal of Pedralli (2004) cannot be considered, and D. campestris Kunth is a “ nomen nudum ”.

Figures

FIG. 3. Dioscorea campestris. A. Staminate inflorescence. B. Secondary staminate inflorescence. C–D. Details of staminate flower. E. Habit. F. Pistillate inflorescence. G. Secondary pistillate inflorescence. H–I. Details of pistillate flower. J. Infructescence. K. Fruit. L. Tuber in apical view. M. Tuber with branch in side view. Scale bar: A = 5 cm; B, C, H, I = 3 mm; D = 1.5 mm; E = 4 cm; F = 1 cm; G = 4 mm; J = 3.5 cm; K = 2.2 cm; L, M = 14 cm.

FIG. 4. Dioscorea campestris. A. Habit. B. Tuber in side view. C. Tuber in apical view. D. Detail of staminate flower. E. Detail of pistillate flower. F. Fruit. Scale bars: A = 2.5 cm; B = 3.5 cm; C = 4.5 cm; D = 1 mm; E = 1.5 mm; F = 1 cm.

FIG. 2. A–D. Cross section showing anatomy of aerial stem and tuber. A and C. Dioscorea campestris. B and D. Dioscorea pedalis. A–B. Aerial stem. Note difference in composition and size of medulla between species. White circles indicate cauline vascular bundles and black circles identify common bundles; white arrows (phloem unit); lv (large vessel); pi (pith). C–D. Tuber. Note brachysclereids (asterisk) in storied cork (sto). Scale bars: A = 150 Mm; B, C = 150 Mm; D = 400 Mm.

FIG. 1. Photomicrographs and electron micrographs of Dioscorea. A–B. Dioscorea campestris. A. Distal polar view (SEM). B. Detailed view of the surface (SEM). Arrow indicates granules. C–F. Dioscorea pedalis. C. Optical section representing the distal polar view. D. Distal polar view (SEM). E. Equatorial view, general appearance. F. Detailed view of the surface (SEM). Arrow indicates smaller lumina around the larger lumina. Scale bars: A, C, D, E = 5 Mm; B, F = 2 Mm.

FIG. 5. Distribution map of Dioscorea campestris and Dioscorea pedalis based on herbarium specimens.