Sicydium nereoi Pozner, 2015

Nicola, Marcela V., Donadío, Sabina & Pozner, Raúl, 2015, A new species of Sicydium (Cucurbitaceae) from Argentina, Phytotaxa 197 (2), pp. 153-156 : 153-155

Sicydium nereoi Pozner sp. nov. ( Fig. 1 )

Type:— ARGENTINA. Prov. Corrientes: Dpto. Esquina, Islas frente a Esquina, 30 November 1974, A. Krapovickas, C. L. Cristóbal, J. Irigoyen & A. Schinini 26905 (holotype CTES!).

Tendrilous, villose-glandulose, diclinous climber. Stems 5-sulcate, densely villose-glandulose. Glandulose trichomes simple, uniseriate, patent, variable in length up to 0.8 mm long, mixed with simple, less frequent, eglandulose trichomes 1.5–2 mm long, more abundant and dense at the nodes. Leaves entire, simple, cordate, up to 4 cm wide × 6 cm long, 7–9-pedately nerved, apex acute-acuminate, margin entire, adaxial surface densely villose, most trichomes simple, eglandulose, abaxial surface villose-glandulose, with simple glandulose and eglandulose trichomes mixed as on the stem, particularly denser on the nerves. Petioles 7–8 mm, densely villose-glandulose. Tendrils distally bifid, coiling below and above the branching point, villose-glandulose at base, becoming almost glabrous towards the distal end. Staminate flowers in axillar, bracteate thyrses up to 7–9 cm long, lower bracts ovate, acute, becoming narrower up to linear towards the distal cymes, bracts and rachis villose-glandulose as the stem but with shorter trichomes, floral pedicels glabrous, ebracteolate, articulate at their very base. Staminate flowers minute, hypanthium saucer-shaped, sepals 5, triangular to long triangular, ca. 0.2 mm wide × 0.8 mm long, margin entire, with some trichomes on the abaxial side, petals 5, triangular to long triangular-acuminate, 0.4–0.5 mm wide × 1–1.8 mm long, with some trichomes on both sides, and along the margin in a ciliated arrangement, inner side of the hypanthium densely covered by glandular trichomes forming a cushion-like trichomatous nectary, stamens 3, one monothecate with horizontal theca, and two bithecous with vertical thecae, filament 0.1–0.15 mm thick, 0.3–0.4 mm long, usually erect in the bithecous stamens and incurved in the monothecous stamen, connective usually wide up to divaricate, thecae 0.2 mm long, longitudinally dehiscent. Carpellate flowers and fruits unknown.

Distribution: — Sicydium nereoi is known only in Corrientes province, in the islands on the Paraná River in front of Esquina city.

Etymology: — Sicydium nereoi is dedicated to Raúl Nereo Martínez Crovetto, Argentinean botanist and professor at “Universidad Nacional del Litoral”, Corrientes, who produced, along his career, the first and most complete research about taxonomy of Cucurbitaceae from Argentina.

Relationships: —Species of Sicydium and Pteropepon share the same staminate flower structure, being distinguished by the 2-winged samara (ovary strongly compressed in the carpellate flower) in Pteropepon versus the globose berries of Sicydium (ovaries not compressed in carpellate flowers). Concerning vegetative characters, species of Pteropepon are usually glabrous with deltoid to 3–5-lobed leaves, versus the hirsute-villose, frequently glandulose pubescence, and entire, cordate leaves of Sicydium . Despite the lack of carpellate flowers and fruits, we decided to describe this new species under Sicydium (and not Pteropepon ) because of its leaf morphology and particular pubescence, so much similar to Sicydium species. The closest morphologically similar species to Sicydium nereoi are S. gracile Cogniaux (1878: 113) from southern Brazil and S. tamnifolium (Kunth in Humboldt, Bonpland & Kunth 1825: 175) Cogniaux in Candolle & Candolle (1881: 905) from Mexico to Peru and Bolivia. Sicydium nereoi is morphologically related to S. tamnifolium by the pubescence and foliar morphology, but differs by the glandulose-pubescent pedicels (glabrous in S. nereoi ), the pedicel articulation at the lower half (versus at the very base of the pedicel in S. nereoi ) and the slightly cup-shaped hypanthium (completely flat and exposed in S. nereoi ). It also differs from S. gracile , by the dense villose-glandulose pubescence (glabrous or short eglandulose in S. gracile ), pedicels articulate at the very base (versus the distal articulation just under the staminate flower in S. gracile ), and the slightly cup-shaped hypanthium (completely flat and exposed in S. nereoi ). There is a third, clearly different species from southern Brazil, S. diffusum Cogniaux (1878: 112) : Sicydium nereoi is densely villose-glandulose with pedicels articulated at the very base, while S. diffusum is almost completely glabrous (but the pedicels) with pedicels articulated on the upper distal half.

Additional specimens examined: — Sicydium gracile Cogn. BRAZIL. Rio Grande do Sul: Montenegro, sarmentum in silva, 500 m, 20 November 1950, A. Sehnem 5057 (SI). Alto Matador, 800 m, 24 November 1958, R. Reitz & R.M. Klein 7598 (CTES). Ibid., 11 September 1958, R. Reitz & R.M. Klein 7074 (CTES). São Leopoldo , in silva primaeva scandens, 17 December 1948, B. Rambo 38907 (LIL 314263). Ibid., 16 October 1935, B. Rambo 1608 (LIL 181090). Ibid., ad montem Sapucaya, in silva primaeva scandens, B. Rambo 37947 (LIL 238145). Porto Alegre, in silva campestri scandens, 1 September 1948, B. Rambo 37489 (LIL 236579). Ibid., 20 November 1948, B. Rambo 38148 (LIL 123994). Ibid., Morro de la Gloria, in silva, 26 October 1945, B. Rambo 29319 (LIL 157554), F. Sellow s.n. (syntypes BR 0000006605087, F 0BN009022, JSTOR images). Sicydium diffusum Cogn. BRAZIL. Amazonas: Rio Negro, “prope Manaos, prov. do Alto Amazona, fl. May”, 3–8 August 1857, R. Spruce 1539 (holotype K000424201, isotypes C10009957, NY00468323, BR0000006605520, JSTOR images). Sicydium tamnifolium (H.B.K.) Cogn. CO- LOMBIA. Antioquia: Guarumo, Río Magdalena, A. Bonpland 1674 (holotype P, JSTOR image).

Figures

FIGURE 1. Sicydium nereoi. A. Habit. B. Stem pubescence. C. Leaf abaxial pubescence. D. Leaf adaxial pubescence. E–F. Staminate flower, side and front view. G. Sepal. H. Petal. I–I’. Bithecal stamen with divaricate connective. Drawn by Francisco Rojas from A. Krapovickas et al. 26905.